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	$218.72	11.485%	$243.84	$243.84	$243.85	$243.80
Purchase #2	$213.97	12.694%	$241.1314	$241.13	$241.15	$241.10
Purchase #3	$152.81	11.796%	$170.8355	$170.84	$170.85	$170.80
Purchase #4	$85.39	4.472%	$89.2086	$89.21	$89.20	$89.20
Purchase #5	$226.98	4.816%	$237.9114	$237.91	$237.90	$237.90
Purchase #6	$75.88	10.638%	$83.9521	$83.95	$83.95	$84.00
Purchase #7	$179.71	9.300%	$196.423	$196.42	$196.40	$196.40
7 purchase totals =	$1,153.46		$1,263.3020	$1,263.30	$1,263.30	$1,263.20