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	$93.27	10.580%	$103.138	$103.14	$103.15	$103.10
Purchase #2	$32.56	6.781%	$34.7679	$34.77	$34.75	$34.80
Purchase #3	$61.95	6.304%	$65.8553	$65.86	$65.85	$65.90
Purchase #4	$18.26	12.802%	$20.5976	$20.60	$20.60	$20.60
Purchase #5	$32.91	7.392%	$35.3427	$35.34	$35.35	$35.30
Purchase #6	$215.75	11.425%	$240.3994	$240.40	$240.40	$240.40
Purchase #7	$58.28	11.244%	$64.833	$64.83	$64.85	$64.80
7 purchase totals =	$512.98		$564.9339	$564.94	$564.95	$564.90