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	$95.57	9.459%	$104.61	$104.61	$104.60	$104.60
Purchase #2	$82.42	3.332%	$85.1662	$85.17	$85.15	$85.20
Purchase #3	$99.35	4.795%	$104.1138	$104.11	$104.10	$104.10
Purchase #4	$8.55	3.672%	$8.864	$8.86	$8.85	$8.90
Purchase #5	$82.44	5.232%	$86.7533	$86.75	$86.75	$86.80
Purchase #6	$139.29	10.391%	$153.7636	$153.76	$153.75	$153.80
Purchase #7	$243.72	8.641%	$264.7798	$264.78	$264.80	$264.80
7 purchase totals =	$751.34		$808.0507	$808.04	$808.00	$808.20