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	$237.34	3.163%	$244.8471	$244.85	$244.85	$244.80
Purchase #2	$62.37	9.831%	$68.5016	$68.50	$68.50	$68.50
Purchase #3	$127.41	12.773%	$143.6841	$143.68	$143.70	$143.70
Purchase #4	$58.81	4.779%	$61.6205	$61.62	$61.60	$61.60
Purchase #5	$148.85	12.546%	$167.5247	$167.52	$167.50	$167.50
Purchase #6	$187.95	8.818%	$204.5234	$204.52	$204.50	$204.50
Purchase #7	$36.69	10.386%	$40.5006	$40.50	$40.50	$40.50
7 purchase totals =	$859.42		$931.2020	$931.19	$931.15	$931.10