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	$106.82	12.407%	$120.0732	$120.07	$120.05	$120.10
Purchase #2	$80.43	10.607%	$88.9612	$88.96	$88.95	$89.00
Purchase #3	$227.98	3.154%	$235.1705	$235.17	$235.15	$235.20
Purchase #4	$188.74	4.221%	$196.7067	$196.71	$196.70	$196.70
Purchase #5	$140.73	3.397%	$145.5106	$145.51	$145.50	$145.50
Purchase #6	$225.84	7.412%	$242.5793	$242.58	$242.60	$242.60
Purchase #7	$82.78	3.734%	$85.871	$85.87	$85.85	$85.90
7 purchase totals =	$1,053.32		$1,114.8725	$1,114.87	$1,114.80	$1,115.00