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	$249.92	7.662%	$269.0689	$269.07	$269.05	$269.10
Purchase #2	$226.89	10.396%	$250.4775	$250.48	$250.50	$250.50
Purchase #3	$72.75	7.744%	$78.3838	$78.38	$78.40	$78.40
Purchase #4	$78.76	13.565%	$89.4438	$89.44	$89.45	$89.40
Purchase #5	$147.78	7.642%	$159.0733	$159.07	$159.05	$159.10
Purchase #6	$138.47	5.554%	$146.1606	$146.16	$146.15	$146.20
Purchase #7	$137.62	12.539%	$154.8762	$154.88	$154.90	$154.90
7 purchase totals =	$1,052.19		$1,147.4841	$1,147.48	$1,147.50	$1,147.60