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	$213.39	5.774%	$225.7111	$225.71	$225.70	$225.70
Purchase #2	$246.74	12.711%	$278.1031	$278.10	$278.10	$278.10
Purchase #3	$99.72	5.746%	$105.4499	$105.45	$105.45	$105.40
Purchase #4	$244.43	7.476%	$262.7036	$262.70	$262.70	$262.70
Purchase #5	$83.37	9.801%	$91.5411	$91.54	$91.55	$91.50
Purchase #6	$77.33	11.528%	$86.2446	$86.24	$86.25	$86.20
Purchase #7	$113.53	8.777%	$123.4945	$123.49	$123.50	$123.50
7 purchase totals =	$1,078.51		$1,173.2479	$1,173.23	$1,173.25	$1,173.10