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	$223.90	11.812%	$250.3471	$250.35	$250.35	$250.30
Purchase #2	$143.33	5.197%	$150.7789	$150.78	$150.80	$150.80
Purchase #3	$94.60	6.349%	$100.6062	$100.61	$100.60	$100.60
Purchase #4	$238.75	10.576%	$264.0002	$264.00	$264.00	$264.00
Purchase #5	$162.75	6.311%	$173.0212	$173.02	$173.00	$173.00
Purchase #6	$156.49	4.254%	$163.1471	$163.15	$163.15	$163.10
Purchase #7	$106.94	4.523%	$111.7769	$111.78	$111.80	$111.80
7 purchase totals =	$1,126.76		$1,213.6776	$1,213.69	$1,213.70	$1,213.60