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	$86.38	10.321%	$95.2953	$95.30	$95.30	$95.30
Purchase #2	$145.46	7.548%	$156.4393	$156.44	$156.45	$156.40
Purchase #3	$143.28	3.672%	$148.5412	$148.54	$148.55	$148.50
Purchase #4	$83.53	13.419%	$94.7389	$94.74	$94.75	$94.70
Purchase #5	$139.37	6.584%	$148.5461	$148.55	$148.55	$148.50
Purchase #6	$139.73	4.604%	$146.1632	$146.16	$146.15	$146.20
Purchase #7	$62.58	13.431%	$70.9851	$70.99	$71.00	$71.00
7 purchase totals =	$800.33		$860.7091	$860.72	$860.75	$860.60