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	$221.81	10.333%	$244.7296	$244.73	$244.75	$244.70
Purchase #2	$31.36	13.405%	$35.5638	$35.56	$35.55	$35.60
Purchase #3	$29.57	10.488%	$32.6713	$32.67	$32.65	$32.70
Purchase #4	$132.73	5.829%	$140.4668	$140.47	$140.45	$140.50
Purchase #5	$10.43	10.677%	$11.5436	$11.54	$11.55	$11.50
Purchase #6	$233.69	12.297%	$262.4269	$262.43	$262.45	$262.40
Purchase #7	$37.86	12.568%	$42.6182	$42.62	$42.60	$42.60
7 purchase totals =	$697.45		$770.0202	$770.02	$770.00	$770.00