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	$228.77	13.694%	$260.0978	$260.10	$260.10	$260.10
Purchase #2	$91.50	8.769%	$99.5236	$99.52	$99.50	$99.50
Purchase #3	$231.51	13.199%	$262.067	$262.07	$262.05	$262.10
Purchase #4	$43.42	5.444%	$45.7838	$45.78	$45.80	$45.80
Purchase #5	$229.26	8.448%	$248.6279	$248.63	$248.65	$248.60
Purchase #6	$102.64	7.110%	$109.9377	$109.94	$109.95	$109.90
Purchase #7	$123.84	10.354%	$136.6624	$136.66	$136.65	$136.70
7 purchase totals =	$1,050.94		$1,162.7002	$1,162.70	$1,162.70	$1,162.70