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	$229.43	13.582%	$260.5912	$260.59	$260.60	$260.60
Purchase #2	$177.57	4.507%	$185.5731	$185.57	$185.55	$185.60
Purchase #3	$75.27	9.660%	$82.5411	$82.54	$82.55	$82.50
Purchase #4	$115.35	12.445%	$129.7053	$129.71	$129.70	$129.70
Purchase #5	$123.72	3.328%	$127.8374	$127.84	$127.85	$127.80
Purchase #6	$202.97	3.763%	$210.6078	$210.61	$210.60	$210.60
Purchase #7	$70.88	7.616%	$76.2782	$76.28	$76.30	$76.30
7 purchase totals =	$995.19		$1,073.1341	$1,073.14	$1,073.15	$1,073.10