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	$81.71	3.665%	$84.7047	$84.70	$84.70	$84.70
Purchase #2	$239.45	12.717%	$269.9009	$269.90	$269.90	$269.90
Purchase #3	$97.27	8.690%	$105.7228	$105.72	$105.70	$105.70
Purchase #4	$224.34	9.508%	$245.6702	$245.67	$245.65	$245.70
Purchase #5	$104.82	6.712%	$111.8555	$111.86	$111.85	$111.90
Purchase #6	$83.82	11.251%	$93.2506	$93.25	$93.25	$93.30
Purchase #7	$90.97	7.194%	$97.5144	$97.51	$97.50	$97.50
7 purchase totals =	$922.38		$1,008.6191	$1,008.61	$1,008.55	$1,008.70