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	$84.57	11.310%	$94.1349	$94.13	$94.15	$94.10
Purchase #2	$158.42	9.825%	$173.9848	$173.98	$174.00	$174.00
Purchase #3	$156.73	10.783%	$173.6302	$173.63	$173.65	$173.60
Purchase #4	$100.68	9.563%	$110.308	$110.31	$110.30	$110.30
Purchase #5	$128.50	11.402%	$143.1516	$143.15	$143.15	$143.20
Purchase #6	$148.31	13.848%	$168.848	$168.85	$168.85	$168.80
Purchase #7	$65.51	10.485%	$72.3787	$72.38	$72.40	$72.40
7 purchase totals =	$842.72		$936.4362	$936.43	$936.50	$936.40