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	$140.28	7.367%	$150.6144	$150.61	$150.60	$150.60
Purchase #2	$49.30	13.829%	$56.1177	$56.12	$56.10	$56.10
Purchase #3	$47.51	4.266%	$49.5368	$49.54	$49.55	$49.50
Purchase #4	$190.27	4.524%	$198.8778	$198.88	$198.90	$198.90
Purchase #5	$139.85	4.712%	$146.4397	$146.44	$146.45	$146.40
Purchase #6	$177.31	9.377%	$193.9364	$193.94	$193.95	$193.90
Purchase #7	$140.54	4.577%	$146.9725	$146.97	$146.95	$147.00
7 purchase totals =	$885.06		$942.4953	$942.50	$942.50	$942.40