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	$187.64	3.777%	$194.7272	$194.73	$194.75	$194.70
Purchase #2	$49.66	7.610%	$53.4391	$53.44	$53.45	$53.40
Purchase #3	$33.34	12.304%	$37.4422	$37.44	$37.45	$37.40
Purchase #4	$31.25	5.251%	$32.8909	$32.89	$32.90	$32.90
Purchase #5	$159.97	5.510%	$168.7843	$168.78	$168.80	$168.80
Purchase #6	$49.52	8.138%	$53.5499	$53.55	$53.55	$53.50
Purchase #7	$180.92	5.275%	$190.4635	$190.46	$190.45	$190.50
7 purchase totals =	$692.30		$731.2971	$731.29	$731.35	$731.20