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	$121.37	4.116%	$126.3656	$126.37	$126.35	$126.40
Purchase #2	$33.76	4.546%	$35.2947	$35.29	$35.30	$35.30
Purchase #3	$160.77	3.210%	$165.9307	$165.93	$165.95	$165.90
Purchase #4	$145.31	13.103%	$164.35	$164.35	$164.35	$164.40
Purchase #5	$199.25	9.581%	$218.3401	$218.34	$218.35	$218.30
Purchase #6	$57.59	4.794%	$60.3509	$60.35	$60.35	$60.40
Purchase #7	$34.41	8.299%	$37.2657	$37.27	$37.25	$37.30
7 purchase totals =	$752.46		$807.8977	$807.90	$807.90	$808.00