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	$110.54	7.855%	$119.2229	$119.22	$119.20	$119.20
Purchase #2	$42.99	12.466%	$48.3491	$48.35	$48.35	$48.30
Purchase #3	$233.77	10.745%	$258.8886	$258.89	$258.90	$258.90
Purchase #4	$155.46	6.441%	$165.4732	$165.47	$165.45	$165.50
Purchase #5	$85.58	12.126%	$95.9574	$95.96	$95.95	$96.00
Purchase #6	$174.85	6.280%	$185.8306	$185.83	$185.85	$185.80
Purchase #7	$29.60	9.824%	$32.5079	$32.51	$32.50	$32.50
7 purchase totals =	$832.79		$906.2297	$906.23	$906.20	$906.20