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	$196.68	7.211%	$210.8626	$210.86	$210.85	$210.90
Purchase #2	$62.32	12.388%	$70.0402	$70.04	$70.05	$70.00
Purchase #3	$201.47	3.852%	$209.2306	$209.23	$209.25	$209.20
Purchase #4	$185.45	11.579%	$206.9233	$206.92	$206.90	$206.90
Purchase #5	$49.33	12.436%	$55.4647	$55.46	$55.45	$55.50
Purchase #6	$186.43	5.190%	$196.1057	$196.11	$196.10	$196.10
Purchase #7	$38.86	4.224%	$40.5014	$40.50	$40.50	$40.50
7 purchase totals =	$920.54		$989.1285	$989.12	$989.10	$989.10