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	$115.33	6.758%	$123.124	$123.12	$123.10	$123.10
Purchase #2	$238.61	10.680%	$264.0935	$264.09	$264.10	$264.10
Purchase #3	$40.35	13.191%	$45.6726	$45.67	$45.65	$45.70
Purchase #4	$31.43	3.593%	$32.5593	$32.56	$32.55	$32.60
Purchase #5	$119.51	10.721%	$132.3227	$132.32	$132.30	$132.30
Purchase #6	$211.42	11.728%	$236.2153	$236.22	$236.20	$236.20
Purchase #7	$229.54	5.837%	$242.9382	$242.94	$242.95	$242.90
7 purchase totals =	$986.19		$1,076.9256	$1,076.92	$1,076.85	$1,076.90