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	$236.91	3.425%	$245.0242	$245.02	$245.00	$245.00
Purchase #2	$30.60	7.555%	$32.9118	$32.91	$32.90	$32.90
Purchase #3	$96.39	9.549%	$105.5943	$105.59	$105.60	$105.60
Purchase #4	$182.39	7.500%	$196.0693	$196.07	$196.05	$196.10
Purchase #5	$226.87	12.770%	$255.8413	$255.84	$255.85	$255.80
Purchase #6	$207.37	8.787%	$225.5916	$225.59	$225.60	$225.60
Purchase #7	$93.74	12.264%	$105.2363	$105.24	$105.25	$105.20
7 purchase totals =	$1,074.27		$1,166.2688	$1,166.26	$1,166.25	$1,166.20