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	$51.41	8.288%	$55.6709	$55.67	$55.65	$55.70
Purchase #2	$156.66	9.429%	$171.4315	$171.43	$171.45	$171.40
Purchase #3	$73.64	13.231%	$83.3833	$83.38	$83.40	$83.40
Purchase #4	$57.35	5.448%	$60.4744	$60.47	$60.45	$60.50
Purchase #5	$23.28	3.609%	$24.1202	$24.12	$24.10	$24.10
Purchase #6	$32.38	5.482%	$34.1551	$34.16	$34.15	$34.20
Purchase #7	$110.65	11.194%	$123.0362	$123.04	$123.05	$123.00
7 purchase totals =	$505.37		$552.2716	$552.27	$552.25	$552.30