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	$127.53	10.522%	$140.9487	$140.95	$140.95	$140.90
Purchase #2	$171.76	11.506%	$191.5227	$191.52	$191.50	$191.50
Purchase #3	$213.98	5.195%	$225.0963	$225.10	$225.10	$225.10
Purchase #4	$233.52	12.653%	$263.0673	$263.07	$263.05	$263.10
Purchase #5	$74.71	8.784%	$81.2725	$81.27	$81.25	$81.30
Purchase #6	$82.76	8.438%	$89.7433	$89.74	$89.75	$89.70
Purchase #7	$30.29	6.158%	$32.1553	$32.16	$32.15	$32.20
7 purchase totals =	$934.55		$1,023.8061	$1,023.81	$1,023.75	$1,023.80