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	$173.86	6.651%	$185.4234	$185.42	$185.40	$185.40
Purchase #2	$175.71	10.463%	$194.0945	$194.09	$194.10	$194.10
Purchase #3	$242.80	5.561%	$256.3021	$256.30	$256.30	$256.30
Purchase #4	$173.66	10.495%	$191.8856	$191.89	$191.90	$191.90
Purchase #5	$84.54	11.583%	$94.3323	$94.33	$94.35	$94.30
Purchase #6	$196.72	6.602%	$209.7075	$209.71	$209.70	$209.70
Purchase #7	$62.49	5.235%	$65.7614	$65.76	$65.75	$65.80
7 purchase totals =	$1,109.78		$1,197.5068	$1,197.50	$1,197.50	$1,197.50