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	$148.34	8.149%	$160.4282	$160.43	$160.45	$160.40
Purchase #2	$14.34	6.115%	$15.2169	$15.22	$15.20	$15.20
Purchase #3	$65.44	9.860%	$71.8924	$71.89	$71.90	$71.90
Purchase #4	$89.89	12.273%	$100.9222	$100.92	$100.90	$100.90
Purchase #5	$170.75	12.230%	$191.6327	$191.63	$191.65	$191.60
Purchase #6	$156.45	8.696%	$170.0549	$170.05	$170.05	$170.10
Purchase #7	$223.46	12.237%	$250.8048	$250.80	$250.80	$250.80
7 purchase totals =	$868.67		$960.9521	$960.94	$960.95	$960.90