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	$243.55	4.647%	$254.8678	$254.87	$254.85	$254.90
Purchase #2	$103.80	8.137%	$112.2462	$112.25	$112.25	$112.20
Purchase #3	$98.73	9.807%	$108.4125	$108.41	$108.40	$108.40
Purchase #4	$229.27	13.456%	$260.1206	$260.12	$260.10	$260.10
Purchase #5	$53.51	11.261%	$59.5358	$59.54	$59.55	$59.50
Purchase #6	$154.37	4.338%	$161.0666	$161.07	$161.05	$161.10
Purchase #7	$167.92	13.749%	$191.0073	$191.01	$191.00	$191.00
7 purchase totals =	$1,051.15		$1,147.2568	$1,147.27	$1,147.20	$1,147.20