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	$106.64	6.159%	$113.208	$113.21	$113.20	$113.20
Purchase #2	$64.55	10.113%	$71.0779	$71.08	$71.10	$71.10
Purchase #3	$34.80	10.243%	$38.3646	$38.36	$38.35	$38.40
Purchase #4	$133.95	7.574%	$144.0954	$144.10	$144.10	$144.10
Purchase #5	$83.58	9.483%	$91.5059	$91.51	$91.50	$91.50
Purchase #6	$109.93	8.494%	$119.2675	$119.27	$119.25	$119.30
Purchase #7	$84.71	4.453%	$88.4821	$88.48	$88.50	$88.50
7 purchase totals =	$618.16		$666.0014	$666.01	$666.00	$666.10