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	$127.42	7.607%	$137.1128	$137.11	$137.10	$137.10
Purchase #2	$229.73	6.280%	$244.157	$244.16	$244.15	$244.20
Purchase #3	$23.82	5.439%	$25.1156	$25.12	$25.10	$25.10
Purchase #4	$212.82	4.234%	$221.8308	$221.83	$221.85	$221.80
Purchase #5	$13.92	6.383%	$14.8085	$14.81	$14.80	$14.80
Purchase #6	$225.57	9.189%	$246.2976	$246.30	$246.30	$246.30
Purchase #7	$189.95	3.421%	$196.4482	$196.45	$196.45	$196.40
7 purchase totals =	$1,023.23		$1,085.7705	$1,085.78	$1,085.75	$1,085.70