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	$35.97	10.835%	$39.8673	$39.87	$39.85	$39.90
Purchase #2	$169.80	6.311%	$180.5161	$180.52	$180.50	$180.50
Purchase #3	$197.34	9.503%	$216.0932	$216.09	$216.10	$216.10
Purchase #4	$64.84	9.653%	$71.099	$71.10	$71.10	$71.10
Purchase #5	$224.46	7.275%	$240.7895	$240.79	$240.80	$240.80
Purchase #6	$94.28	11.661%	$105.274	$105.27	$105.25	$105.30
Purchase #7	$153.71	12.148%	$172.3827	$172.38	$172.40	$172.40
7 purchase totals =	$940.40		$1,026.0218	$1,026.02	$1,026.00	$1,026.10