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	$94.62	13.522%	$107.4145	$107.41	$107.40	$107.40
Purchase #2	$126.92	8.227%	$137.3617	$137.36	$137.35	$137.40
Purchase #3	$115.31	10.735%	$127.6885	$127.69	$127.70	$127.70
Purchase #4	$132.39	10.408%	$146.1692	$146.17	$146.15	$146.20
Purchase #5	$90.61	13.478%	$102.8224	$102.82	$102.80	$102.80
Purchase #6	$40.43	13.789%	$46.0049	$46.00	$46.00	$46.00
Purchase #7	$73.55	6.496%	$78.3278	$78.33	$78.35	$78.30
7 purchase totals =	$673.83		$745.7890	$745.78	$745.75	$745.80