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	$243.69	8.604%	$264.6571	$264.66	$264.65	$264.70
Purchase #2	$75.74	3.653%	$78.5068	$78.51	$78.50	$78.50
Purchase #3	$50.83	10.454%	$56.1438	$56.14	$56.15	$56.10
Purchase #4	$173.53	9.186%	$189.4705	$189.47	$189.45	$189.50
Purchase #5	$82.37	9.630%	$90.3022	$90.30	$90.30	$90.30
Purchase #6	$145.71	11.244%	$162.0936	$162.09	$162.10	$162.10
Purchase #7	$219.32	7.827%	$236.4862	$236.49	$236.50	$236.50
7 purchase totals =	$991.19		$1,077.6602	$1,077.66	$1,077.65	$1,077.70