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	$168.94	13.301%	$191.4107	$191.41	$191.40	$191.40
Purchase #2	$99.64	13.532%	$113.1233	$113.12	$113.10	$113.10
Purchase #3	$245.29	3.859%	$254.7557	$254.76	$254.75	$254.80
Purchase #4	$25.53	8.572%	$27.7184	$27.72	$27.70	$27.70
Purchase #5	$19.50	3.337%	$20.1507	$20.15	$20.15	$20.20
Purchase #6	$200.85	13.344%	$227.6514	$227.65	$227.65	$227.70
Purchase #7	$102.42	8.756%	$111.3879	$111.39	$111.40	$111.40
7 purchase totals =	$862.17		$946.1981	$946.20	$946.15	$946.30