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	$175.94	6.697%	$187.7227	$187.72	$187.70	$187.70
Purchase #2	$189.93	3.582%	$196.7333	$196.73	$196.75	$196.70
Purchase #3	$29.77	9.653%	$32.6437	$32.64	$32.65	$32.60
Purchase #4	$164.36	3.511%	$170.1307	$170.13	$170.15	$170.10
Purchase #5	$58.66	9.576%	$64.2773	$64.28	$64.30	$64.30
Purchase #6	$26.77	6.565%	$28.5275	$28.53	$28.55	$28.50
Purchase #7	$98.51	13.341%	$111.6522	$111.65	$111.65	$111.70
7 purchase totals =	$743.94		$791.6874	$791.68	$791.75	$791.60