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	$73.79	7.705%	$79.4755	$79.48	$79.50	$79.50
Purchase #2	$234.93	11.199%	$261.2398	$261.24	$261.25	$261.20
Purchase #3	$243.52	11.577%	$271.7123	$271.71	$271.70	$271.70
Purchase #4	$30.36	6.235%	$32.2529	$32.25	$32.25	$32.30
Purchase #5	$55.78	12.540%	$62.7748	$62.77	$62.75	$62.80
Purchase #6	$152.92	13.462%	$173.5061	$173.51	$173.50	$173.50
Purchase #7	$136.48	11.769%	$152.5423	$152.54	$152.55	$152.50
7 purchase totals =	$927.78		$1,033.5037	$1,033.50	$1,033.50	$1,033.50