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	$59.56	9.552%	$65.2492	$65.25	$65.25	$65.20
Purchase #2	$143.80	7.723%	$154.9057	$154.91	$154.90	$154.90
Purchase #3	$145.28	13.723%	$165.2168	$165.22	$165.20	$165.20
Purchase #4	$96.77	13.725%	$110.0517	$110.05	$110.05	$110.10
Purchase #5	$175.34	12.230%	$196.7841	$196.78	$196.80	$196.80
Purchase #6	$190.93	4.333%	$199.203	$199.20	$199.20	$199.20
Purchase #7	$166.69	11.104%	$185.1993	$185.20	$185.20	$185.20
7 purchase totals =	$978.37		$1,076.6098	$1,076.61	$1,076.60	$1,076.60