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	$54.98	11.403%	$61.2494	$61.25	$61.25	$61.20
Purchase #2	$174.53	12.500%	$196.3463	$196.35	$196.35	$196.30
Purchase #3	$57.89	13.623%	$65.7764	$65.78	$65.80	$65.80
Purchase #4	$131.46	9.137%	$143.4715	$143.47	$143.45	$143.50
Purchase #5	$244.61	13.674%	$278.058	$278.06	$278.05	$278.10
Purchase #6	$92.43	8.225%	$100.0324	$100.03	$100.05	$100.00
Purchase #7	$122.31	7.269%	$131.2007	$131.20	$131.20	$131.20
7 purchase totals =	$878.21		$976.1347	$976.14	$976.15	$976.10