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	$242.91	8.501%	$263.5598	$263.56	$263.55	$263.60
Purchase #2	$40.82	13.845%	$46.4715	$46.47	$46.45	$46.50
Purchase #3	$148.87	11.705%	$166.2952	$166.30	$166.30	$166.30
Purchase #4	$44.79	4.662%	$46.8781	$46.88	$46.90	$46.90
Purchase #5	$211.42	5.853%	$223.7944	$223.79	$223.80	$223.80
Purchase #6	$99.61	11.277%	$110.843	$110.84	$110.85	$110.80
Purchase #7	$211.95	11.540%	$236.409	$236.41	$236.40	$236.40
7 purchase totals =	$1,000.37		$1,094.2510	$1,094.25	$1,094.25	$1,094.30