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	$136.86	13.714%	$155.629	$155.63	$155.65	$155.60
Purchase #2	$90.60	3.783%	$94.0274	$94.03	$94.05	$94.00
Purchase #3	$234.33	11.859%	$262.1192	$262.12	$262.10	$262.10
Purchase #4	$157.71	5.117%	$165.78	$165.78	$165.80	$165.80
Purchase #5	$128.80	9.311%	$140.7926	$140.79	$140.80	$140.80
Purchase #6	$180.45	7.118%	$193.2944	$193.29	$193.30	$193.30
Purchase #7	$91.82	8.474%	$99.6008	$99.60	$99.60	$99.60
7 purchase totals =	$1,020.57		$1,111.2434	$1,111.24	$1,111.30	$1,111.20