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	$52.87	12.835%	$59.6559	$59.66	$59.65	$59.70
Purchase #2	$188.94	13.205%	$213.8895	$213.89	$213.90	$213.90
Purchase #3	$111.46	3.503%	$115.3644	$115.36	$115.35	$115.40
Purchase #4	$133.41	13.463%	$151.371	$151.37	$151.35	$151.40
Purchase #5	$158.68	8.230%	$171.7394	$171.74	$171.75	$171.70
Purchase #6	$105.47	3.476%	$109.1361	$109.14	$109.15	$109.10
Purchase #7	$51.32	7.799%	$55.3224	$55.32	$55.30	$55.30
7 purchase totals =	$802.15		$876.4787	$876.48	$876.45	$876.50