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	$135.32	4.605%	$141.5515	$141.55	$141.55	$141.60
Purchase #2	$123.83	5.364%	$130.4722	$130.47	$130.45	$130.50
Purchase #3	$161.92	3.129%	$166.9865	$166.99	$167.00	$167.00
Purchase #4	$155.73	9.863%	$171.0896	$171.09	$171.10	$171.10
Purchase #5	$65.28	3.114%	$67.3128	$67.31	$67.30	$67.30
Purchase #6	$154.31	11.328%	$171.7902	$171.79	$171.80	$171.80
Purchase #7	$139.70	5.593%	$147.5134	$147.51	$147.50	$147.50
7 purchase totals =	$936.09		$996.7162	$996.71	$996.70	$996.80