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	$110.49	11.450%	$123.1411	$123.14	$123.15	$123.10
Purchase #2	$162.73	10.180%	$179.2959	$179.30	$179.30	$179.30
Purchase #3	$90.48	3.381%	$93.5391	$93.54	$93.55	$93.50
Purchase #4	$53.70	7.372%	$57.6588	$57.66	$57.65	$57.70
Purchase #5	$136.93	13.783%	$155.8031	$155.80	$155.80	$155.80
Purchase #6	$109.92	12.722%	$123.904	$123.90	$123.90	$123.90
Purchase #7	$29.93	9.373%	$32.7353	$32.74	$32.75	$32.70
7 purchase totals =	$694.18		$766.0773	$766.08	$766.10	$766.00