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	$220.61	6.145%	$234.1665	$234.17	$234.15	$234.20
Purchase #2	$134.78	3.620%	$139.659	$139.66	$139.65	$139.70
Purchase #3	$214.69	10.338%	$236.8847	$236.88	$236.90	$236.90
Purchase #4	$150.76	7.611%	$162.2343	$162.23	$162.25	$162.20
Purchase #5	$197.44	9.605%	$216.4041	$216.40	$216.40	$216.40
Purchase #6	$18.26	3.287%	$18.8602	$18.86	$18.85	$18.90
Purchase #7	$89.90	12.240%	$100.9038	$100.90	$100.90	$100.90
7 purchase totals =	$1,026.44		$1,109.1126	$1,109.10	$1,109.10	$1,109.20