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	$108.76	4.195%	$113.3225	$113.32	$113.30	$113.30
Purchase #2	$219.60	13.161%	$248.5016	$248.50	$248.50	$248.50
Purchase #3	$188.41	5.505%	$198.782	$198.78	$198.80	$198.80
Purchase #4	$234.79	5.644%	$248.0415	$248.04	$248.05	$248.00
Purchase #5	$177.39	10.694%	$196.3601	$196.36	$196.35	$196.40
Purchase #6	$109.42	5.485%	$115.4217	$115.42	$115.40	$115.40
Purchase #7	$175.55	11.844%	$196.3421	$196.34	$196.35	$196.30
7 purchase totals =	$1,213.92		$1,316.7715	$1,316.76	$1,316.75	$1,316.70