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	$199.78	4.552%	$208.874	$208.87	$208.85	$208.90
Purchase #2	$223.30	11.677%	$249.3747	$249.37	$249.35	$249.40
Purchase #3	$192.26	13.132%	$217.5076	$217.51	$217.50	$217.50
Purchase #4	$226.43	7.124%	$242.5609	$242.56	$242.55	$242.60
Purchase #5	$242.33	13.546%	$275.156	$275.16	$275.15	$275.20
Purchase #6	$68.81	4.571%	$71.9553	$71.96	$71.95	$72.00
Purchase #7	$87.49	13.771%	$99.5382	$99.54	$99.55	$99.50
7 purchase totals =	$1,240.40		$1,364.9667	$1,364.97	$1,364.90	$1,365.10