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	$11.73	9.865%	$12.8872	$12.89	$12.90	$12.90
Purchase #2	$22.77	12.581%	$25.6347	$25.63	$25.65	$25.60
Purchase #3	$13.34	11.418%	$14.8632	$14.86	$14.85	$14.90
Purchase #4	$62.37	10.419%	$68.8683	$68.87	$68.85	$68.90
Purchase #5	$56.80	5.152%	$59.7263	$59.73	$59.75	$59.70
Purchase #6	$121.54	3.222%	$125.456	$125.46	$125.45	$125.50
Purchase #7	$135.68	7.222%	$145.4788	$145.48	$145.50	$145.50
7 purchase totals =	$424.23		$452.9145	$452.92	$452.95	$453.00