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	$226.46	12.318%	$254.3553	$254.36	$254.35	$254.40
Purchase #2	$6.94	11.573%	$7.7432	$7.74	$7.75	$7.70
Purchase #3	$88.58	13.862%	$100.859	$100.86	$100.85	$100.90
Purchase #4	$69.27	4.784%	$72.5839	$72.58	$72.60	$72.60
Purchase #5	$50.63	4.645%	$52.9818	$52.98	$53.00	$53.00
Purchase #6	$65.90	6.260%	$70.0253	$70.03	$70.05	$70.00
Purchase #7	$172.83	7.670%	$186.0861	$186.09	$186.10	$186.10
7 purchase totals =	$680.61		$744.6346	$744.64	$744.70	$744.70