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	$123.69	5.701%	$130.7416	$130.74	$130.75	$130.70
Purchase #2	$154.40	10.467%	$170.561	$170.56	$170.55	$170.60
Purchase #3	$131.33	9.854%	$144.2713	$144.27	$144.25	$144.30
Purchase #4	$132.44	8.541%	$143.7517	$143.75	$143.75	$143.80
Purchase #5	$75.39	10.446%	$83.2652	$83.27	$83.25	$83.30
Purchase #6	$242.53	5.210%	$255.1658	$255.17	$255.15	$255.20
Purchase #7	$147.95	5.872%	$156.6376	$156.64	$156.65	$156.60
7 purchase totals =	$1,007.73		$1,084.3942	$1,084.40	$1,084.35	$1,084.50