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	$216.48	11.208%	$240.7431	$240.74	$240.75	$240.70
Purchase #2	$40.93	11.243%	$45.5318	$45.53	$45.55	$45.50
Purchase #3	$57.50	13.107%	$65.0365	$65.04	$65.05	$65.00
Purchase #4	$83.66	13.318%	$94.8018	$94.80	$94.80	$94.80
Purchase #5	$142.69	6.738%	$152.3045	$152.30	$152.30	$152.30
Purchase #6	$31.59	11.873%	$35.3407	$35.34	$35.35	$35.30
Purchase #7	$119.28	4.261%	$124.3625	$124.36	$124.35	$124.40
7 purchase totals =	$692.13		$758.1209	$758.11	$758.15	$758.00