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	$193.82	9.312%	$211.8685	$211.87	$211.85	$211.90
Purchase #2	$138.81	10.102%	$152.8326	$152.83	$152.85	$152.80
Purchase #3	$248.50	5.330%	$261.7451	$261.75	$261.75	$261.70
Purchase #4	$90.71	9.345%	$99.1868	$99.19	$99.20	$99.20
Purchase #5	$184.98	13.623%	$210.1798	$210.18	$210.20	$210.20
Purchase #6	$174.46	4.104%	$181.6198	$181.62	$181.60	$181.60
Purchase #7	$191.33	13.185%	$216.5569	$216.56	$216.55	$216.60
7 purchase totals =	$1,222.61		$1,333.9895	$1,334.00	$1,334.00	$1,334.00