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	$133.25	12.688%	$150.1568	$150.16	$150.15	$150.20
Purchase #2	$89.56	12.472%	$100.7299	$100.73	$100.75	$100.70
Purchase #3	$69.58	12.621%	$78.3617	$78.36	$78.35	$78.40
Purchase #4	$43.79	4.234%	$45.6441	$45.64	$45.65	$45.60
Purchase #5	$93.36	8.811%	$101.5859	$101.59	$101.60	$101.60
Purchase #6	$193.41	6.512%	$206.0049	$206.00	$206.00	$206.00
Purchase #7	$216.86	13.843%	$246.8799	$246.88	$246.90	$246.90
7 purchase totals =	$839.81		$929.3632	$929.36	$929.40	$929.40