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	$53.83	10.778%	$59.6318	$59.63	$59.65	$59.60
Purchase #2	$117.70	10.773%	$130.3798	$130.38	$130.40	$130.40
Purchase #3	$197.55	13.259%	$223.7432	$223.74	$223.75	$223.70
Purchase #4	$212.97	4.472%	$222.494	$222.49	$222.50	$222.50
Purchase #5	$219.26	3.573%	$227.0942	$227.09	$227.10	$227.10
Purchase #6	$162.66	6.277%	$172.8702	$172.87	$172.85	$172.90
Purchase #7	$248.72	10.424%	$274.6466	$274.65	$274.65	$274.60
7 purchase totals =	$1,212.69		$1,310.8598	$1,310.85	$1,310.90	$1,310.80