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	$140.61	7.109%	$150.606	$150.61	$150.60	$150.60
Purchase #2	$98.76	6.696%	$105.373	$105.37	$105.35	$105.40
Purchase #3	$135.53	5.704%	$143.2606	$143.26	$143.25	$143.30
Purchase #4	$55.50	10.464%	$61.3075	$61.31	$61.30	$61.30
Purchase #5	$211.71	13.340%	$239.9521	$239.95	$239.95	$240.00
Purchase #6	$223.55	4.802%	$234.2849	$234.28	$234.30	$234.30
Purchase #7	$29.88	12.488%	$33.6114	$33.61	$33.60	$33.60
7 purchase totals =	$895.54		$968.3955	$968.39	$968.35	$968.50