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	$41.28	3.464%	$42.7099	$42.71	$42.70	$42.70
Purchase #2	$113.75	4.664%	$119.0553	$119.06	$119.05	$119.10
Purchase #3	$159.77	12.225%	$179.3019	$179.30	$179.30	$179.30
Purchase #4	$231.33	10.492%	$255.6011	$255.60	$255.60	$255.60
Purchase #5	$224.75	11.588%	$250.794	$250.79	$250.80	$250.80
Purchase #6	$90.47	12.624%	$101.8909	$101.89	$101.90	$101.90
Purchase #7	$106.79	4.586%	$111.6874	$111.69	$111.70	$111.70
7 purchase totals =	$968.14		$1,061.0405	$1,061.04	$1,061.05	$1,061.10