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	$112.72	5.113%	$118.4834	$118.48	$118.50	$118.50
Purchase #2	$196.33	5.404%	$206.9397	$206.94	$206.95	$206.90
Purchase #3	$159.77	3.343%	$165.1111	$165.11	$165.10	$165.10
Purchase #4	$135.70	11.217%	$150.9215	$150.92	$150.90	$150.90
Purchase #5	$121.26	13.135%	$137.1875	$137.19	$137.20	$137.20
Purchase #6	$165.40	7.513%	$177.8265	$177.83	$177.85	$177.80
Purchase #7	$209.58	6.465%	$223.1293	$223.13	$223.15	$223.10
7 purchase totals =	$1,100.76		$1,179.5990	$1,179.60	$1,179.65	$1,179.50