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	$31.38	11.104%	$34.8644	$34.86	$34.85	$34.90
Purchase #2	$67.80	3.513%	$70.1818	$70.18	$70.20	$70.20
Purchase #3	$96.46	6.635%	$102.8601	$102.86	$102.85	$102.90
Purchase #4	$124.77	4.422%	$130.2873	$130.29	$130.30	$130.30
Purchase #5	$197.31	7.710%	$212.5226	$212.52	$212.50	$212.50
Purchase #6	$249.84	13.188%	$282.7889	$282.79	$282.80	$282.80
Purchase #7	$216.33	5.405%	$228.0226	$228.02	$228.00	$228.00
7 purchase totals =	$983.89		$1,061.5277	$1,061.52	$1,061.50	$1,061.60