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	$22.87	6.633%	$24.387	$24.39	$24.40	$24.40
Purchase #2	$50.52	3.149%	$52.1109	$52.11	$52.10	$52.10
Purchase #3	$27.44	7.557%	$29.5136	$29.51	$29.50	$29.50
Purchase #4	$173.45	4.865%	$181.8883	$181.89	$181.90	$181.90
Purchase #5	$141.86	9.428%	$155.2346	$155.23	$155.25	$155.20
Purchase #6	$196.73	6.572%	$209.6591	$209.66	$209.65	$209.70
Purchase #7	$218.87	6.654%	$233.4336	$233.43	$233.45	$233.40
7 purchase totals =	$831.74		$886.2271	$886.22	$886.25	$886.20