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	$241.99	11.314%	$269.3687	$269.37	$269.35	$269.40
Purchase #2	$80.76	12.468%	$90.8292	$90.83	$90.85	$90.80
Purchase #3	$150.64	3.389%	$155.7452	$155.75	$155.75	$155.70
Purchase #4	$150.60	8.178%	$162.9161	$162.92	$162.90	$162.90
Purchase #5	$248.36	6.475%	$264.4413	$264.44	$264.45	$264.40
Purchase #6	$243.57	7.251%	$261.2313	$261.23	$261.25	$261.20
Purchase #7	$180.27	6.218%	$191.4792	$191.48	$191.50	$191.50
7 purchase totals =	$1,296.19		$1,396.0110	$1,396.02	$1,396.05	$1,395.90