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	$195.57	11.225%	$217.5227	$217.52	$217.50	$217.50
Purchase #2	$241.84	9.197%	$264.082	$264.08	$264.10	$264.10
Purchase #3	$152.39	6.493%	$162.2847	$162.28	$162.30	$162.30
Purchase #4	$250.57	5.533%	$264.434	$264.43	$264.45	$264.40
Purchase #5	$28.69	12.144%	$32.1741	$32.17	$32.15	$32.20
Purchase #6	$158.31	4.474%	$165.3928	$165.39	$165.40	$165.40
Purchase #7	$107.50	4.340%	$112.1655	$112.17	$112.15	$112.20
7 purchase totals =	$1,134.87		$1,218.0558	$1,218.04	$1,218.05	$1,218.10