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	$70.52	11.467%	$78.6065	$78.61	$78.60	$78.60
Purchase #2	$182.32	13.157%	$206.3078	$206.31	$206.30	$206.30
Purchase #3	$9.88	4.514%	$10.326	$10.33	$10.35	$10.30
Purchase #4	$188.58	3.373%	$194.9408	$194.94	$194.95	$194.90
Purchase #5	$35.58	6.575%	$37.9194	$37.92	$37.90	$37.90
Purchase #6	$235.45	7.476%	$253.0522	$253.05	$253.05	$253.10
Purchase #7	$204.92	12.768%	$231.0842	$231.08	$231.10	$231.10
7 purchase totals =	$927.25		$1,012.2369	$1,012.24	$1,012.25	$1,012.20