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	$168.39	3.643%	$174.5244	$174.52	$174.50	$174.50
Purchase #2	$143.98	11.400%	$160.3937	$160.39	$160.40	$160.40
Purchase #3	$196.42	8.415%	$212.9487	$212.95	$212.95	$212.90
Purchase #4	$209.70	7.215%	$224.8299	$224.83	$224.85	$224.80
Purchase #5	$52.56	5.698%	$55.5549	$55.55	$55.55	$55.60
Purchase #6	$57.76	13.432%	$65.5183	$65.52	$65.50	$65.50
Purchase #7	$29.49	12.462%	$33.165	$33.17	$33.15	$33.20
7 purchase totals =	$858.30		$926.9349	$926.93	$926.90	$926.90