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	$241.52	3.331%	$249.565	$249.57	$249.55	$249.60
Purchase #2	$215.85	6.355%	$229.5673	$229.57	$229.55	$229.60
Purchase #3	$98.50	8.228%	$106.6046	$106.60	$106.60	$106.60
Purchase #4	$65.77	7.132%	$70.4607	$70.46	$70.45	$70.50
Purchase #5	$32.35	7.248%	$34.6947	$34.69	$34.70	$34.70
Purchase #6	$132.69	6.427%	$141.218	$141.22	$141.20	$141.20
Purchase #7	$191.61	9.215%	$209.2669	$209.27	$209.25	$209.30
7 purchase totals =	$978.29		$1,041.3772	$1,041.38	$1,041.30	$1,041.50