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	$30.47	5.508%	$32.1483	$32.15	$32.15	$32.10
Purchase #2	$160.28	13.471%	$181.8713	$181.87	$181.85	$181.90
Purchase #3	$75.93	13.176%	$85.9345	$85.93	$85.95	$85.90
Purchase #4	$112.70	13.528%	$127.9461	$127.95	$127.95	$127.90
Purchase #5	$150.38	5.783%	$159.0765	$159.08	$159.10	$159.10
Purchase #6	$130.45	9.555%	$142.9145	$142.91	$142.90	$142.90
Purchase #7	$210.25	8.796%	$228.7436	$228.74	$228.75	$228.70
7 purchase totals =	$870.46		$958.6348	$958.63	$958.65	$958.50