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	$152.90	8.723%	$166.2375	$166.24	$166.25	$166.20
Purchase #2	$120.83	5.832%	$127.8768	$127.88	$127.90	$127.90
Purchase #3	$201.61	4.799%	$211.2853	$211.29	$211.30	$211.30
Purchase #4	$162.32	4.494%	$169.6147	$169.61	$169.60	$169.60
Purchase #5	$166.34	11.547%	$185.5473	$185.55	$185.55	$185.50
Purchase #6	$154.89	4.482%	$161.8322	$161.83	$161.85	$161.80
Purchase #7	$236.92	3.708%	$245.705	$245.71	$245.70	$245.70
7 purchase totals =	$1,195.81		$1,268.0988	$1,268.11	$1,268.15	$1,268.00