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	$232.46	4.165%	$242.142	$242.14	$242.15	$242.10
Purchase #2	$81.54	10.746%	$90.3023	$90.30	$90.30	$90.30
Purchase #3	$157.43	10.130%	$173.3777	$173.38	$173.40	$173.40
Purchase #4	$63.65	11.368%	$70.8857	$70.89	$70.90	$70.90
Purchase #5	$196.93	10.793%	$218.1847	$218.18	$218.20	$218.20
Purchase #6	$99.47	11.455%	$110.8643	$110.86	$110.85	$110.90
Purchase #7	$239.28	8.110%	$258.6856	$258.69	$258.70	$258.70
7 purchase totals =	$1,070.76		$1,164.4423	$1,164.44	$1,164.50	$1,164.50