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	$55.81	13.400%	$63.2885	$63.29	$63.30	$63.30
Purchase #2	$112.68	7.334%	$120.944	$120.94	$120.95	$120.90
Purchase #3	$172.78	7.322%	$185.431	$185.43	$185.45	$185.40
Purchase #4	$158.76	13.301%	$179.8767	$179.88	$179.90	$179.90
Purchase #5	$60.42	8.350%	$65.4651	$65.47	$65.45	$65.50
Purchase #6	$193.45	3.701%	$200.6096	$200.61	$200.60	$200.60
Purchase #7	$230.83	5.176%	$242.7778	$242.78	$242.80	$242.80
7 purchase totals =	$984.73		$1,058.3927	$1,058.40	$1,058.45	$1,058.40