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	$80.84	5.782%	$85.5142	$85.51	$85.50	$85.50
Purchase #2	$12.74	11.371%	$14.1887	$14.19	$14.20	$14.20
Purchase #3	$206.38	6.850%	$220.517	$220.52	$220.50	$220.50
Purchase #4	$113.91	4.785%	$119.3606	$119.36	$119.35	$119.40
Purchase #5	$185.40	7.240%	$198.823	$198.82	$198.80	$198.80
Purchase #6	$86.52	3.473%	$89.5248	$89.52	$89.50	$89.50
Purchase #7	$95.60	10.282%	$105.4296	$105.43	$105.45	$105.40
7 purchase totals =	$781.39		$833.3579	$833.35	$833.30	$833.30