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	$99.91	8.330%	$108.2325	$108.23	$108.25	$108.20
Purchase #2	$65.90	8.779%	$71.6854	$71.69	$71.70	$71.70
Purchase #3	$46.78	12.469%	$52.613	$52.61	$52.60	$52.60
Purchase #4	$19.41	3.770%	$20.1418	$20.14	$20.15	$20.10
Purchase #5	$75.33	3.184%	$77.7285	$77.73	$77.75	$77.70
Purchase #6	$59.51	13.124%	$67.3201	$67.32	$67.30	$67.30
Purchase #7	$68.62	10.192%	$75.6138	$75.61	$75.60	$75.60
7 purchase totals =	$435.46		$473.3351	$473.33	$473.35	$473.20