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	$153.85	9.126%	$167.8904	$167.89	$167.90	$167.90
Purchase #2	$229.89	9.388%	$251.4721	$251.47	$251.45	$251.50
Purchase #3	$215.71	13.112%	$243.9939	$243.99	$244.00	$244.00
Purchase #4	$43.61	10.323%	$48.1119	$48.11	$48.10	$48.10
Purchase #5	$163.89	13.817%	$186.5347	$186.53	$186.55	$186.50
Purchase #6	$134.56	11.652%	$150.2389	$150.24	$150.25	$150.20
Purchase #7	$200.46	11.333%	$223.1781	$223.18	$223.20	$223.20
7 purchase totals =	$1,141.97		$1,271.4200	$1,271.41	$1,271.45	$1,271.40