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	$181.53	13.428%	$205.9058	$205.91	$205.90	$205.90
Purchase #2	$84.43	6.720%	$90.1037	$90.10	$90.10	$90.10
Purchase #3	$102.88	5.851%	$108.8995	$108.90	$108.90	$108.90
Purchase #4	$44.82	7.453%	$48.1604	$48.16	$48.15	$48.20
Purchase #5	$148.35	4.320%	$154.7587	$154.76	$154.75	$154.80
Purchase #6	$85.78	9.664%	$94.0698	$94.07	$94.05	$94.10
Purchase #7	$125.70	13.290%	$142.4055	$142.41	$142.40	$142.40
7 purchase totals =	$773.49		$844.3034	$844.31	$844.25	$844.40