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	$60.71	4.608%	$63.5075	$63.51	$63.50	$63.50
Purchase #2	$85.76	5.633%	$90.5909	$90.59	$90.60	$90.60
Purchase #3	$191.60	13.115%	$216.7283	$216.73	$216.75	$216.70
Purchase #4	$103.30	7.452%	$110.9979	$111.00	$111.00	$111.00
Purchase #5	$62.60	12.575%	$70.472	$70.47	$70.45	$70.50
Purchase #6	$83.62	6.591%	$89.1314	$89.13	$89.15	$89.10
Purchase #7	$216.43	8.541%	$234.9153	$234.92	$234.90	$234.90
7 purchase totals =	$804.02		$876.3433	$876.35	$876.35	$876.30