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	$68.58	6.568%	$73.0843	$73.08	$73.10	$73.10
Purchase #2	$129.84	9.298%	$141.9125	$141.91	$141.90	$141.90
Purchase #3	$93.27	13.521%	$105.881	$105.88	$105.90	$105.90
Purchase #4	$59.70	4.632%	$62.4653	$62.47	$62.45	$62.50
Purchase #5	$224.61	9.494%	$245.9345	$245.93	$245.95	$245.90
Purchase #6	$94.57	4.709%	$99.0233	$99.02	$99.00	$99.00
Purchase #7	$150.98	4.763%	$158.1712	$158.17	$158.15	$158.20
7 purchase totals =	$821.55		$886.4721	$886.46	$886.45	$886.50