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	$184.55	4.788%	$193.3863	$193.39	$193.40	$193.40
Purchase #2	$102.55	9.286%	$112.0728	$112.07	$112.05	$112.10
Purchase #3	$31.52	7.682%	$33.9414	$33.94	$33.95	$33.90
Purchase #4	$94.28	5.387%	$99.3589	$99.36	$99.35	$99.40
Purchase #5	$51.32	11.335%	$57.1371	$57.14	$57.15	$57.10
Purchase #6	$72.67	8.105%	$78.5599	$78.56	$78.55	$78.60
Purchase #7	$129.93	6.306%	$138.1234	$138.12	$138.10	$138.10
7 purchase totals =	$666.82		$712.5798	$712.58	$712.55	$712.60