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	$141.37	4.845%	$148.2194	$148.22	$148.20	$148.20
Purchase #2	$162.96	13.513%	$184.9808	$184.98	$185.00	$185.00
Purchase #3	$60.77	6.324%	$64.6131	$64.61	$64.60	$64.60
Purchase #4	$79.39	13.765%	$90.318	$90.32	$90.30	$90.30
Purchase #5	$50.89	6.735%	$54.3174	$54.32	$54.30	$54.30
Purchase #6	$46.99	6.448%	$50.0199	$50.02	$50.00	$50.00
Purchase #7	$208.48	13.352%	$236.3162	$236.32	$236.30	$236.30
7 purchase totals =	$750.85		$828.7848	$828.79	$828.70	$828.70