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	$68.31	4.176%	$71.1626	$71.16	$71.15	$71.20
Purchase #2	$11.28	3.151%	$11.6354	$11.64	$11.65	$11.60
Purchase #3	$179.74	12.419%	$202.0619	$202.06	$202.05	$202.10
Purchase #4	$203.80	9.646%	$223.4585	$223.46	$223.45	$223.50
Purchase #5	$234.52	8.349%	$254.1001	$254.10	$254.10	$254.10
Purchase #6	$131.41	10.609%	$145.3513	$145.35	$145.35	$145.40
Purchase #7	$165.54	4.229%	$172.5407	$172.54	$172.55	$172.50
7 purchase totals =	$994.60		$1,080.3105	$1,080.31	$1,080.30	$1,080.40