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	$212.37	7.641%	$228.5972	$228.60	$228.60	$228.60
Purchase #2	$39.97	6.240%	$42.4641	$42.46	$42.45	$42.50
Purchase #3	$108.29	10.533%	$119.6962	$119.70	$119.70	$119.70
Purchase #4	$83.78	12.850%	$94.5457	$94.55	$94.55	$94.50
Purchase #5	$33.74	4.214%	$35.1618	$35.16	$35.15	$35.20
Purchase #6	$86.93	4.577%	$90.9088	$90.91	$90.90	$90.90
Purchase #7	$149.85	10.421%	$165.4659	$165.47	$165.45	$165.50
7 purchase totals =	$714.93		$776.8397	$776.85	$776.80	$776.90