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	$236.69	5.172%	$248.9316	$248.93	$248.95	$248.90
Purchase #2	$23.72	11.116%	$26.3567	$26.36	$26.35	$26.40
Purchase #3	$119.50	3.587%	$123.7865	$123.79	$123.80	$123.80
Purchase #4	$165.94	4.131%	$172.795	$172.80	$172.80	$172.80
Purchase #5	$144.98	11.205%	$161.225	$161.23	$161.25	$161.20
Purchase #6	$55.94	7.123%	$59.9246	$59.92	$59.90	$59.90
Purchase #7	$85.48	7.160%	$91.6004	$91.60	$91.60	$91.60
7 purchase totals =	$832.25		$884.6198	$884.63	$884.65	$884.60