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	$200.34	11.568%	$223.5153	$223.52	$223.50	$223.50
Purchase #2	$23.34	11.811%	$26.0967	$26.10	$26.10	$26.10
Purchase #3	$111.60	9.571%	$122.2812	$122.28	$122.30	$122.30
Purchase #4	$130.94	6.193%	$139.0491	$139.05	$139.05	$139.00
Purchase #5	$235.43	8.146%	$254.6081	$254.61	$254.60	$254.60
Purchase #6	$170.43	12.519%	$191.7661	$191.77	$191.75	$191.80
Purchase #7	$84.79	6.419%	$90.2327	$90.23	$90.25	$90.20
7 purchase totals =	$956.87		$1,047.5492	$1,047.56	$1,047.55	$1,047.50