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	$169.76	10.635%	$187.814	$187.81	$187.80	$187.80
Purchase #2	$247.31	8.760%	$268.9744	$268.97	$268.95	$269.00
Purchase #3	$233.71	5.717%	$247.0712	$247.07	$247.05	$247.10
Purchase #4	$131.89	4.563%	$137.9081	$137.91	$137.90	$137.90
Purchase #5	$219.89	9.160%	$240.0319	$240.03	$240.05	$240.00
Purchase #6	$172.48	13.675%	$196.0666	$196.07	$196.05	$196.10
Purchase #7	$18.63	12.106%	$20.8853	$20.89	$20.90	$20.90
7 purchase totals =	$1,193.67		$1,298.7515	$1,298.75	$1,298.70	$1,298.80