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	$61.53	6.611%	$65.5977	$65.60	$65.60	$65.60
Purchase #2	$202.71	12.351%	$227.7467	$227.75	$227.75	$227.70
Purchase #3	$198.37	11.717%	$221.613	$221.61	$221.60	$221.60
Purchase #4	$239.57	10.160%	$263.9103	$263.91	$263.90	$263.90
Purchase #5	$53.93	10.141%	$59.399	$59.40	$59.40	$59.40
Purchase #6	$110.55	12.595%	$124.4738	$124.47	$124.45	$124.50
Purchase #7	$37.92	8.211%	$41.0336	$41.03	$41.05	$41.00
7 purchase totals =	$904.58		$1,003.7741	$1,003.77	$1,003.75	$1,003.70