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	$82.62	11.271%	$91.9321	$91.93	$91.95	$91.90
Purchase #2	$89.40	4.741%	$93.6385	$93.64	$93.65	$93.60
Purchase #3	$122.41	13.237%	$138.6134	$138.61	$138.60	$138.60
Purchase #4	$233.33	9.842%	$256.2943	$256.29	$256.30	$256.30
Purchase #5	$195.63	6.499%	$208.344	$208.34	$208.35	$208.30
Purchase #6	$103.89	8.218%	$112.4277	$112.43	$112.45	$112.40
Purchase #7	$88.30	11.594%	$98.5375	$98.54	$98.55	$98.50
7 purchase totals =	$915.58		$999.7875	$999.78	$999.85	$999.60