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	$180.25	10.285%	$198.7887	$198.79	$198.80	$198.80
Purchase #2	$160.48	12.790%	$181.0054	$181.01	$181.00	$181.00
Purchase #3	$67.59	13.675%	$76.8329	$76.83	$76.85	$76.80
Purchase #4	$10.93	7.468%	$11.7463	$11.75	$11.75	$11.70
Purchase #5	$169.72	12.869%	$191.5613	$191.56	$191.55	$191.60
Purchase #6	$229.59	3.740%	$238.1767	$238.18	$238.20	$238.20
Purchase #7	$234.51	8.404%	$254.2182	$254.22	$254.20	$254.20
7 purchase totals =	$1,053.07		$1,152.3295	$1,152.34	$1,152.35	$1,152.30