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	$183.25	7.684%	$197.3309	$197.33	$197.35	$197.30
Purchase #2	$57.42	11.755%	$64.1697	$64.17	$64.15	$64.20
Purchase #3	$174.49	6.334%	$185.5422	$185.54	$185.55	$185.50
Purchase #4	$169.71	9.449%	$185.7459	$185.75	$185.75	$185.70
Purchase #5	$62.60	7.518%	$67.3063	$67.31	$67.30	$67.30
Purchase #6	$130.28	12.495%	$146.5585	$146.56	$146.55	$146.60
Purchase #7	$157.50	10.809%	$174.5242	$174.52	$174.50	$174.50
7 purchase totals =	$935.25		$1,021.1777	$1,021.18	$1,021.15	$1,021.10