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	$127.78	3.279%	$131.9699	$131.97	$131.95	$132.00
Purchase #2	$181.67	13.305%	$205.8412	$205.84	$205.85	$205.80
Purchase #3	$212.61	13.847%	$242.0501	$242.05	$242.05	$242.10
Purchase #4	$12.36	5.558%	$13.047	$13.05	$13.05	$13.00
Purchase #5	$164.43	12.240%	$184.5562	$184.56	$184.55	$184.60
Purchase #6	$157.31	10.364%	$173.6136	$173.61	$173.60	$173.60
Purchase #7	$80.54	3.171%	$83.0939	$83.09	$83.10	$83.10
7 purchase totals =	$936.70		$1,034.1719	$1,034.17	$1,034.15	$1,034.20