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	$129.72	7.571%	$139.5411	$139.54	$139.55	$139.50
Purchase #2	$231.88	4.282%	$241.8091	$241.81	$241.80	$241.80
Purchase #3	$144.71	4.681%	$151.4839	$151.48	$151.50	$151.50
Purchase #4	$84.45	13.784%	$96.0906	$96.09	$96.10	$96.10
Purchase #5	$173.45	8.411%	$188.0389	$188.04	$188.05	$188.00
Purchase #6	$172.86	4.176%	$180.0786	$180.08	$180.10	$180.10
Purchase #7	$145.48	7.263%	$156.0462	$156.05	$156.05	$156.00
7 purchase totals =	$1,082.55		$1,153.0884	$1,153.09	$1,153.15	$1,153.00