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	$89.30	6.537%	$95.1375	$95.14	$95.15	$95.10
Purchase #2	$165.29	10.591%	$182.7959	$182.80	$182.80	$182.80
Purchase #3	$26.41	8.683%	$28.7032	$28.70	$28.70	$28.70
Purchase #4	$222.46	10.569%	$245.9718	$245.97	$245.95	$246.00
Purchase #5	$53.30	11.770%	$59.5734	$59.57	$59.55	$59.60
Purchase #6	$39.25	7.598%	$42.2322	$42.23	$42.25	$42.20
Purchase #7	$26.44	5.565%	$27.9114	$27.91	$27.90	$27.90
7 purchase totals =	$622.45		$682.3254	$682.32	$682.30	$682.30