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	$161.85	12.216%	$181.6216	$181.62	$181.60	$181.60
Purchase #2	$37.39	9.276%	$40.8583	$40.86	$40.85	$40.90
Purchase #3	$15.81	3.299%	$16.3316	$16.33	$16.35	$16.30
Purchase #4	$99.91	9.854%	$109.7551	$109.76	$109.75	$109.80
Purchase #5	$88.94	11.110%	$98.8212	$98.82	$98.80	$98.80
Purchase #6	$208.58	5.556%	$220.1687	$220.17	$220.15	$220.20
Purchase #7	$29.56	12.487%	$33.2512	$33.25	$33.25	$33.30
7 purchase totals =	$642.04		$700.8077	$700.81	$700.75	$700.90