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	$50.59	6.459%	$53.8576	$53.86	$53.85	$53.90
Purchase #2	$250.51	8.349%	$271.4251	$271.43	$271.45	$271.40
Purchase #3	$59.41	4.540%	$62.1072	$62.11	$62.10	$62.10
Purchase #4	$9.47	13.205%	$10.7205	$10.72	$10.70	$10.70
Purchase #5	$232.91	10.812%	$258.0922	$258.09	$258.10	$258.10
Purchase #6	$98.33	7.728%	$105.9289	$105.93	$105.95	$105.90
Purchase #7	$172.57	3.323%	$178.3045	$178.30	$178.30	$178.30
7 purchase totals =	$873.79		$940.4360	$940.44	$940.45	$940.40