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	$171.45	13.637%	$194.8306	$194.83	$194.85	$194.80
Purchase #2	$148.78	7.779%	$160.3536	$160.35	$160.35	$160.40
Purchase #3	$209.49	9.438%	$229.2617	$229.26	$229.25	$229.30
Purchase #4	$12.79	13.427%	$14.5073	$14.51	$14.50	$14.50
Purchase #5	$142.34	4.194%	$148.3097	$148.31	$148.30	$148.30
Purchase #6	$7.37	7.552%	$7.9266	$7.93	$7.95	$7.90
Purchase #7	$123.36	3.152%	$127.2483	$127.25	$127.25	$127.20
7 purchase totals =	$815.58		$882.4378	$882.44	$882.45	$882.40