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	$112.74	5.499%	$118.9396	$118.94	$118.95	$118.90
Purchase #2	$64.81	3.569%	$67.1231	$67.12	$67.10	$67.10
Purchase #3	$148.79	7.296%	$159.6457	$159.65	$159.65	$159.60
Purchase #4	$30.40	9.680%	$33.3427	$33.34	$33.35	$33.30
Purchase #5	$80.33	12.481%	$90.356	$90.36	$90.35	$90.40
Purchase #6	$143.71	4.859%	$150.6929	$150.69	$150.70	$150.70
Purchase #7	$78.86	11.749%	$88.1253	$88.13	$88.15	$88.10
7 purchase totals =	$659.64		$708.2253	$708.23	$708.25	$708.10