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	$156.62	11.231%	$174.21	$174.21	$174.20	$174.20
Purchase #2	$79.85	11.819%	$89.2875	$89.29	$89.30	$89.30
Purchase #3	$133.90	12.246%	$150.2974	$150.30	$150.30	$150.30
Purchase #4	$48.69	11.836%	$54.4529	$54.45	$54.45	$54.50
Purchase #5	$59.90	7.125%	$64.1679	$64.17	$64.15	$64.20
Purchase #6	$161.79	10.617%	$178.9672	$178.97	$178.95	$179.00
Purchase #7	$159.75	12.347%	$179.4743	$179.47	$179.45	$179.50
7 purchase totals =	$800.50		$890.8572	$890.86	$890.80	$891.00