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	$119.39	7.453%	$128.2881	$128.29	$128.30	$128.30
Purchase #2	$184.88	6.573%	$197.0322	$197.03	$197.05	$197.00
Purchase #3	$122.92	7.113%	$131.6633	$131.66	$131.65	$131.70
Purchase #4	$182.68	7.575%	$196.518	$196.52	$196.50	$196.50
Purchase #5	$12.60	13.556%	$14.3081	$14.31	$14.30	$14.30
Purchase #6	$99.39	4.788%	$104.1488	$104.15	$104.15	$104.10
Purchase #7	$243.63	7.385%	$261.6221	$261.62	$261.60	$261.60
7 purchase totals =	$965.49		$1,033.5806	$1,033.58	$1,033.55	$1,033.50