Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$195.55	13.555%	$222.0568	$222.06	$222.05	$222.10
Purchase #2	$172.35	10.190%	$189.9125	$189.91	$189.90	$189.90
Purchase #3	$218.69	6.236%	$232.3275	$232.33	$232.35	$232.30
Purchase #4	$240.55	13.498%	$273.0194	$273.02	$273.00	$273.00
Purchase #5	$170.56	6.109%	$180.9795	$180.98	$181.00	$181.00
Purchase #6	$123.79	5.379%	$130.4487	$130.45	$130.45	$130.40
Purchase #7	$102.25	13.869%	$116.4311	$116.43	$116.45	$116.40
7 purchase totals =	$1,223.74		$1,345.1755	$1,345.18	$1,345.20	$1,345.10