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	$43.33	11.158%	$48.1648	$48.16	$48.15	$48.20
Purchase #2	$89.83	10.755%	$99.4912	$99.49	$99.50	$99.50
Purchase #3	$68.73	13.792%	$78.2092	$78.21	$78.20	$78.20
Purchase #4	$93.65	4.336%	$97.7107	$97.71	$97.70	$97.70
Purchase #5	$66.48	11.108%	$73.8646	$73.86	$73.85	$73.90
Purchase #6	$174.71	3.641%	$181.0712	$181.07	$181.05	$181.10
Purchase #7	$211.89	11.354%	$235.948	$235.95	$235.95	$235.90
7 purchase totals =	$748.62		$814.4597	$814.45	$814.40	$814.50