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	$195.93	11.421%	$218.3072	$218.31	$218.30	$218.30
Purchase #2	$211.98	10.652%	$234.5601	$234.56	$234.55	$234.60
Purchase #3	$54.41	3.379%	$56.2485	$56.25	$56.25	$56.20
Purchase #4	$14.53	3.499%	$15.0384	$15.04	$15.05	$15.00
Purchase #5	$50.69	10.611%	$56.0687	$56.07	$56.05	$56.10
Purchase #6	$37.84	11.549%	$42.2101	$42.21	$42.20	$42.20
Purchase #7	$40.42	4.612%	$42.2842	$42.28	$42.30	$42.30
7 purchase totals =	$605.80		$664.7172	$664.72	$664.70	$664.70