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	$230.93	9.755%	$253.4572	$253.46	$253.45	$253.50
Purchase #2	$105.48	13.689%	$119.9192	$119.92	$119.90	$119.90
Purchase #3	$122.43	7.219%	$131.2682	$131.27	$131.25	$131.30
Purchase #4	$114.43	5.109%	$120.2762	$120.28	$120.30	$120.30
Purchase #5	$186.63	3.732%	$193.595	$193.60	$193.60	$193.60
Purchase #6	$156.67	10.350%	$172.8853	$172.89	$172.90	$172.90
Purchase #7	$153.46	8.251%	$166.122	$166.12	$166.10	$166.10
7 purchase totals =	$1,070.03		$1,157.5231	$1,157.54	$1,157.50	$1,157.60