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	$40.39	12.356%	$45.3806	$45.38	$45.40	$45.40
Purchase #2	$136.55	4.827%	$143.1413	$143.14	$143.15	$143.10
Purchase #3	$74.79	3.258%	$77.2267	$77.23	$77.25	$77.20
Purchase #4	$55.54	13.544%	$63.0623	$63.06	$63.05	$63.10
Purchase #5	$17.47	5.245%	$18.3863	$18.39	$18.40	$18.40
Purchase #6	$146.60	13.137%	$165.8588	$165.86	$165.85	$165.90
Purchase #7	$57.92	7.112%	$62.0393	$62.04	$62.05	$62.00
7 purchase totals =	$529.26		$575.0953	$575.10	$575.15	$575.10