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	$13.60	6.839%	$14.5301	$14.53	$14.55	$14.50
Purchase #2	$110.54	10.753%	$122.4264	$122.43	$122.45	$122.40
Purchase #3	$46.73	3.761%	$48.4875	$48.49	$48.50	$48.50
Purchase #4	$52.53	7.513%	$56.4766	$56.48	$56.50	$56.50
Purchase #5	$104.50	6.353%	$111.1389	$111.14	$111.15	$111.10
Purchase #6	$249.81	9.494%	$273.527	$273.53	$273.55	$273.50
Purchase #7	$197.91	12.194%	$222.0431	$222.04	$222.05	$222.00
7 purchase totals =	$775.62		$848.6296	$848.64	$848.75	$848.50