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	$102.47	13.328%	$116.1272	$116.13	$116.15	$116.10
Purchase #2	$217.49	13.839%	$247.5884	$247.59	$247.60	$247.60
Purchase #3	$183.56	13.557%	$208.4452	$208.45	$208.45	$208.40
Purchase #4	$64.46	11.506%	$71.8768	$71.88	$71.90	$71.90
Purchase #5	$143.97	8.752%	$156.5703	$156.57	$156.55	$156.60
Purchase #6	$165.95	8.372%	$179.8433	$179.84	$179.85	$179.80
Purchase #7	$245.59	3.234%	$253.5324	$253.53	$253.55	$253.50
7 purchase totals =	$1,123.49		$1,233.9836	$1,233.99	$1,234.05	$1,233.90