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	$204.49	13.405%	$231.9019	$231.90	$231.90	$231.90
Purchase #2	$113.74	12.148%	$127.5571	$127.56	$127.55	$127.60
Purchase #3	$68.33	12.427%	$76.8214	$76.82	$76.80	$76.80
Purchase #4	$47.91	12.361%	$53.8322	$53.83	$53.85	$53.80
Purchase #5	$239.50	3.488%	$247.8538	$247.85	$247.85	$247.90
Purchase #6	$102.65	7.427%	$110.2738	$110.27	$110.25	$110.30
Purchase #7	$176.60	5.204%	$185.7903	$185.79	$185.80	$185.80
7 purchase totals =	$953.22		$1,034.0305	$1,034.02	$1,034.00	$1,034.10