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	$88.30	6.223%	$93.7949	$93.79	$93.80	$93.80
Purchase #2	$57.32	4.153%	$59.7005	$59.70	$59.70	$59.70
Purchase #3	$57.51	6.134%	$61.0377	$61.04	$61.05	$61.00
Purchase #4	$170.86	4.504%	$178.5555	$178.56	$178.55	$178.60
Purchase #5	$139.78	5.495%	$147.4609	$147.46	$147.45	$147.50
Purchase #6	$114.46	5.557%	$120.8205	$120.82	$120.80	$120.80
Purchase #7	$114.53	4.576%	$119.7709	$119.77	$119.75	$119.80
7 purchase totals =	$742.76		$781.1409	$781.14	$781.10	$781.20