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	$115.51	7.807%	$124.5279	$124.53	$124.55	$124.50
Purchase #2	$71.33	9.679%	$78.234	$78.23	$78.25	$78.20
Purchase #3	$206.78	7.360%	$221.999	$222.00	$222.00	$222.00
Purchase #4	$103.71	7.465%	$111.452	$111.45	$111.45	$111.50
Purchase #5	$226.63	8.701%	$246.3491	$246.35	$246.35	$246.30
Purchase #6	$220.27	5.563%	$232.5236	$232.52	$232.50	$232.50
Purchase #7	$173.83	6.417%	$184.9847	$184.98	$185.00	$185.00
7 purchase totals =	$1,118.06		$1,200.0703	$1,200.06	$1,200.10	$1,200.00