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	$245.78	7.731%	$264.7813	$264.78	$264.80	$264.80
Purchase #2	$28.90	11.840%	$32.3218	$32.32	$32.30	$32.30
Purchase #3	$225.82	5.517%	$238.2785	$238.28	$238.30	$238.30
Purchase #4	$21.56	3.194%	$22.2486	$22.25	$22.25	$22.20
Purchase #5	$35.95	4.613%	$37.6084	$37.61	$37.60	$37.60
Purchase #6	$185.29	3.764%	$192.2643	$192.26	$192.25	$192.30
Purchase #7	$241.88	4.761%	$253.3959	$253.40	$253.40	$253.40
7 purchase totals =	$985.18		$1,040.8988	$1,040.90	$1,040.90	$1,040.90