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	$222.45	5.314%	$234.271	$234.27	$234.25	$234.30
Purchase #2	$236.89	5.416%	$249.72	$249.72	$249.70	$249.70
Purchase #3	$90.79	12.245%	$101.9072	$101.91	$101.90	$101.90
Purchase #4	$73.35	13.562%	$83.2977	$83.30	$83.30	$83.30
Purchase #5	$66.48	7.406%	$71.4035	$71.40	$71.40	$71.40
Purchase #6	$177.74	13.770%	$202.2148	$202.21	$202.20	$202.20
Purchase #7	$31.73	13.131%	$35.8965	$35.90	$35.90	$35.90
7 purchase totals =	$899.43		$978.7107	$978.71	$978.65	$978.70