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	$93.51	3.230%	$96.5304	$96.53	$96.55	$96.50
Purchase #2	$59.47	8.357%	$64.4399	$64.44	$64.45	$64.40
Purchase #3	$78.26	6.512%	$83.3563	$83.36	$83.35	$83.40
Purchase #4	$202.85	9.554%	$222.2303	$222.23	$222.25	$222.20
Purchase #5	$38.74	11.356%	$43.1393	$43.14	$43.15	$43.10
Purchase #6	$243.62	4.856%	$255.4502	$255.45	$255.45	$255.50
Purchase #7	$38.29	5.140%	$40.2581	$40.26	$40.25	$40.30
7 purchase totals =	$754.74		$805.4045	$805.41	$805.45	$805.40