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	$152.63	9.267%	$166.7742	$166.77	$166.75	$166.80
Purchase #2	$140.56	11.373%	$156.5459	$156.55	$156.55	$156.50
Purchase #3	$83.62	8.199%	$90.476	$90.48	$90.50	$90.50
Purchase #4	$76.83	9.288%	$83.966	$83.97	$83.95	$84.00
Purchase #5	$146.38	9.805%	$160.7326	$160.73	$160.75	$160.70
Purchase #6	$237.37	7.481%	$255.1276	$255.13	$255.15	$255.10
Purchase #7	$189.25	4.549%	$197.859	$197.86	$197.85	$197.90
7 purchase totals =	$1,026.64		$1,111.4813	$1,111.49	$1,111.50	$1,111.50