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	$216.30	9.581%	$237.0237	$237.02	$237.00	$237.00
Purchase #2	$38.52	8.307%	$41.7199	$41.72	$41.70	$41.70
Purchase #3	$52.77	6.552%	$56.2275	$56.23	$56.25	$56.20
Purchase #4	$91.25	7.190%	$97.8109	$97.81	$97.80	$97.80
Purchase #5	$113.89	12.739%	$128.3984	$128.40	$128.40	$128.40
Purchase #6	$56.30	5.512%	$59.4033	$59.40	$59.40	$59.40
Purchase #7	$52.28	6.199%	$55.5208	$55.52	$55.50	$55.50
7 purchase totals =	$621.31		$676.1045	$676.10	$676.05	$676.00