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	$173.68	9.458%	$190.1067	$190.11	$190.10	$190.10
Purchase #2	$83.79	12.301%	$94.097	$94.10	$94.10	$94.10
Purchase #3	$85.50	6.277%	$90.8668	$90.87	$90.85	$90.90
Purchase #4	$146.45	7.115%	$156.8699	$156.87	$156.85	$156.90
Purchase #5	$114.89	8.358%	$124.4925	$124.49	$124.50	$124.50
Purchase #6	$55.77	12.366%	$62.6665	$62.67	$62.65	$62.70
Purchase #7	$166.26	4.830%	$174.2904	$174.29	$174.30	$174.30
7 purchase totals =	$826.34		$893.3898	$893.40	$893.35	$893.50