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	$110.69	5.578%	$116.8643	$116.86	$116.85	$116.90
Purchase #2	$113.33	8.729%	$123.2226	$123.22	$123.20	$123.20
Purchase #3	$53.71	11.580%	$59.9296	$59.93	$59.95	$59.90
Purchase #4	$209.34	7.841%	$225.7543	$225.75	$225.75	$225.80
Purchase #5	$36.44	5.859%	$38.575	$38.58	$38.60	$38.60
Purchase #6	$76.66	3.582%	$79.406	$79.41	$79.40	$79.40
Purchase #7	$208.28	11.300%	$231.8156	$231.82	$231.80	$231.80
7 purchase totals =	$808.45		$875.5674	$875.57	$875.55	$875.60