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	$52.50	10.567%	$58.0477	$58.05	$58.05	$58.00
Purchase #2	$221.50	11.454%	$246.8706	$246.87	$246.85	$246.90
Purchase #3	$205.74	13.355%	$233.2166	$233.22	$233.20	$233.20
Purchase #4	$168.35	11.266%	$187.3163	$187.32	$187.30	$187.30
Purchase #5	$17.67	3.530%	$18.2938	$18.29	$18.30	$18.30
Purchase #6	$190.89	10.771%	$211.4508	$211.45	$211.45	$211.50
Purchase #7	$233.57	3.281%	$241.2334	$241.23	$241.25	$241.20
7 purchase totals =	$1,090.22		$1,196.4292	$1,196.43	$1,196.40	$1,196.40