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	$92.96	11.726%	$103.8605	$103.86	$103.85	$103.90
Purchase #2	$83.40	5.614%	$88.0821	$88.08	$88.10	$88.10
Purchase #3	$174.96	12.819%	$197.3881	$197.39	$197.40	$197.40
Purchase #4	$98.65	5.414%	$103.9909	$103.99	$104.00	$104.00
Purchase #5	$130.75	8.156%	$141.414	$141.41	$141.40	$141.40
Purchase #6	$78.42	6.786%	$83.7416	$83.74	$83.75	$83.70
Purchase #7	$113.88	12.344%	$127.9373	$127.94	$127.95	$127.90
7 purchase totals =	$773.02		$846.4145	$846.41	$846.45	$846.40