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	$150.81	7.456%	$162.0544	$162.05	$162.05	$162.10
Purchase #2	$188.82	13.110%	$213.5743	$213.57	$213.55	$213.60
Purchase #3	$182.97	9.778%	$200.8608	$200.86	$200.85	$200.90
Purchase #4	$72.46	9.408%	$79.277	$79.28	$79.30	$79.30
Purchase #5	$190.73	3.201%	$196.8353	$196.84	$196.85	$196.80
Purchase #6	$122.51	12.798%	$138.1888	$138.19	$138.20	$138.20
Purchase #7	$104.36	5.339%	$109.9318	$109.93	$109.95	$109.90
7 purchase totals =	$1,012.66		$1,100.7224	$1,100.72	$1,100.75	$1,100.80