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	$197.32	13.441%	$223.8418	$223.84	$223.85	$223.80
Purchase #2	$236.63	9.334%	$258.717	$258.72	$258.70	$258.70
Purchase #3	$38.63	4.562%	$40.3923	$40.39	$40.40	$40.40
Purchase #4	$51.63	3.291%	$53.3291	$53.33	$53.35	$53.30
Purchase #5	$129.80	8.613%	$140.9797	$140.98	$141.00	$141.00
Purchase #6	$112.45	13.321%	$127.4295	$127.43	$127.45	$127.40
Purchase #7	$99.97	6.262%	$106.2301	$106.23	$106.25	$106.20
7 purchase totals =	$866.43		$950.9195	$950.92	$951.00	$950.80