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	$223.38	3.235%	$230.6063	$230.61	$230.60	$230.60
Purchase #2	$165.62	3.649%	$171.6635	$171.66	$171.65	$171.70
Purchase #3	$231.37	5.266%	$243.5539	$243.55	$243.55	$243.60
Purchase #4	$165.75	4.613%	$173.396	$173.40	$173.40	$173.40
Purchase #5	$202.34	4.366%	$211.1742	$211.17	$211.15	$211.20
Purchase #6	$215.54	12.628%	$242.7584	$242.76	$242.75	$242.80
Purchase #7	$80.71	10.681%	$89.3306	$89.33	$89.35	$89.30
7 purchase totals =	$1,284.71		$1,362.4829	$1,362.48	$1,362.45	$1,362.60