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	$88.73	5.251%	$93.3892	$93.39	$93.40	$93.40
Purchase #2	$136.83	3.866%	$142.1198	$142.12	$142.10	$142.10
Purchase #3	$210.60	9.168%	$229.9078	$229.91	$229.90	$229.90
Purchase #4	$242.86	4.489%	$253.762	$253.76	$253.75	$253.80
Purchase #5	$247.63	7.204%	$265.4693	$265.47	$265.45	$265.50
Purchase #6	$50.95	5.225%	$53.6121	$53.61	$53.60	$53.60
Purchase #7	$146.29	3.662%	$151.6471	$151.65	$151.65	$151.60
7 purchase totals =	$1,123.89		$1,189.9073	$1,189.91	$1,189.85	$1,189.90