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	$208.83	6.519%	$222.4436	$222.44	$222.45	$222.40
Purchase #2	$10.88	7.729%	$11.7209	$11.72	$11.70	$11.70
Purchase #3	$131.37	4.209%	$136.8994	$136.90	$136.90	$136.90
Purchase #4	$172.42	4.658%	$180.4513	$180.45	$180.45	$180.50
Purchase #5	$215.73	7.125%	$231.1008	$231.10	$231.10	$231.10
Purchase #6	$172.66	11.144%	$191.9012	$191.90	$191.90	$191.90
Purchase #7	$136.26	7.392%	$146.3323	$146.33	$146.35	$146.30
7 purchase totals =	$1,048.15		$1,120.8495	$1,120.84	$1,120.85	$1,120.80