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	$164.26	12.187%	$184.2784	$184.28	$184.30	$184.30
Purchase #2	$245.34	4.392%	$256.1153	$256.12	$256.10	$256.10
Purchase #3	$21.66	13.526%	$24.5897	$24.59	$24.60	$24.60
Purchase #4	$144.85	3.741%	$150.2688	$150.27	$150.25	$150.30
Purchase #5	$195.41	8.644%	$212.3012	$212.30	$212.30	$212.30
Purchase #6	$141.86	9.695%	$155.6133	$155.61	$155.60	$155.60
Purchase #7	$110.48	5.613%	$116.6812	$116.68	$116.70	$116.70
7 purchase totals =	$1,023.86		$1,099.8479	$1,099.85	$1,099.85	$1,099.90