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	$159.38	7.833%	$171.8642	$171.86	$171.85	$171.90
Purchase #2	$206.62	10.672%	$228.6705	$228.67	$228.65	$228.70
Purchase #3	$99.27	12.133%	$111.3144	$111.31	$111.30	$111.30
Purchase #4	$55.63	12.850%	$62.7785	$62.78	$62.80	$62.80
Purchase #5	$189.62	13.560%	$215.3325	$215.33	$215.35	$215.30
Purchase #6	$156.61	13.754%	$178.1501	$178.15	$178.15	$178.20
Purchase #7	$190.76	4.830%	$199.9737	$199.97	$199.95	$200.00
7 purchase totals =	$1,057.89		$1,168.0839	$1,168.07	$1,168.05	$1,168.20