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	$235.28	3.495%	$243.503	$243.50	$243.50	$243.50
Purchase #2	$134.81	4.166%	$140.4262	$140.43	$140.45	$140.40
Purchase #3	$101.73	3.411%	$105.2	$105.20	$105.20	$105.20
Purchase #4	$78.29	13.675%	$88.9962	$89.00	$89.00	$89.00
Purchase #5	$57.63	8.505%	$62.5314	$62.53	$62.55	$62.50
Purchase #6	$103.79	11.454%	$115.6781	$115.68	$115.70	$115.70
Purchase #7	$247.35	5.688%	$261.4193	$261.42	$261.40	$261.40
7 purchase totals =	$958.88		$1,017.7542	$1,017.76	$1,017.80	$1,017.70