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	$46.49	13.677%	$52.8484	$52.85	$52.85	$52.80
Purchase #2	$181.52	12.155%	$203.5838	$203.58	$203.60	$203.60
Purchase #3	$138.77	5.688%	$146.6632	$146.66	$146.65	$146.70
Purchase #4	$99.29	10.584%	$109.7989	$109.80	$109.80	$109.80
Purchase #5	$42.44	11.508%	$47.324	$47.32	$47.30	$47.30
Purchase #6	$55.83	6.772%	$59.6108	$59.61	$59.60	$59.60
Purchase #7	$207.53	3.293%	$214.364	$214.36	$214.35	$214.40
7 purchase totals =	$771.87		$834.1931	$834.18	$834.15	$834.20