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	$172.95	5.504%	$182.4692	$182.47	$182.45	$182.50
Purchase #2	$103.44	8.167%	$111.8879	$111.89	$111.90	$111.90
Purchase #3	$214.69	6.432%	$228.4989	$228.50	$228.50	$228.50
Purchase #4	$67.70	5.320%	$71.3016	$71.30	$71.30	$71.30
Purchase #5	$223.57	7.687%	$240.7558	$240.76	$240.75	$240.80
Purchase #6	$56.37	10.330%	$62.193	$62.19	$62.20	$62.20
Purchase #7	$114.88	10.457%	$126.893	$126.89	$126.90	$126.90
7 purchase totals =	$953.60		$1,023.9994	$1,024.00	$1,024.00	$1,024.10