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	$150.86	7.632%	$162.3736	$162.37	$162.35	$162.40
Purchase #2	$199.29	3.806%	$206.875	$206.88	$206.90	$206.90
Purchase #3	$95.69	6.383%	$101.7979	$101.80	$101.80	$101.80
Purchase #4	$43.48	3.846%	$45.1522	$45.15	$45.15	$45.20
Purchase #5	$168.88	12.237%	$189.5458	$189.55	$189.55	$189.50
Purchase #6	$248.79	9.371%	$272.1041	$272.10	$272.10	$272.10
Purchase #7	$109.61	8.258%	$118.6616	$118.66	$118.65	$118.70
7 purchase totals =	$1,016.60		$1,096.5102	$1,096.51	$1,096.50	$1,096.60