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	$181.54	4.237%	$189.2318	$189.23	$189.25	$189.20
Purchase #2	$86.92	13.693%	$98.822	$98.82	$98.80	$98.80
Purchase #3	$41.78	13.666%	$47.4897	$47.49	$47.50	$47.50
Purchase #4	$111.83	11.670%	$124.8806	$124.88	$124.90	$124.90
Purchase #5	$106.45	13.502%	$120.8229	$120.82	$120.80	$120.80
Purchase #6	$224.71	13.659%	$255.4031	$255.40	$255.40	$255.40
Purchase #7	$10.49	4.214%	$10.932	$10.93	$10.95	$10.90
7 purchase totals =	$763.72		$847.5821	$847.57	$847.60	$847.50