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	$81.32	9.851%	$89.3308	$89.33	$89.35	$89.30
Purchase #2	$237.81	11.228%	$264.5113	$264.51	$264.50	$264.50
Purchase #3	$37.59	8.562%	$40.8085	$40.81	$40.80	$40.80
Purchase #4	$159.73	4.331%	$166.6479	$166.65	$166.65	$166.60
Purchase #5	$186.70	3.513%	$193.2588	$193.26	$193.25	$193.30
Purchase #6	$43.85	4.245%	$45.7114	$45.71	$45.70	$45.70
Purchase #7	$200.46	9.339%	$219.181	$219.18	$219.20	$219.20
7 purchase totals =	$947.46		$1,019.4497	$1,019.45	$1,019.45	$1,019.40