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	$51.87	7.247%	$55.629	$55.63	$55.65	$55.60
Purchase #2	$38.75	6.603%	$41.3087	$41.31	$41.30	$41.30
Purchase #3	$81.52	12.245%	$91.5021	$91.50	$91.50	$91.50
Purchase #4	$250.89	9.591%	$274.9529	$274.95	$274.95	$275.00
Purchase #5	$101.82	10.519%	$112.5304	$112.53	$112.55	$112.50
Purchase #6	$67.33	7.139%	$72.1367	$72.14	$72.15	$72.10
Purchase #7	$11.98	10.257%	$13.2088	$13.21	$13.20	$13.20
7 purchase totals =	$604.16		$661.2686	$661.27	$661.30	$661.20