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	$96.79	12.693%	$109.0756	$109.08	$109.10	$109.10
Purchase #2	$47.55	13.495%	$53.9669	$53.97	$53.95	$54.00
Purchase #3	$162.61	9.145%	$177.4807	$177.48	$177.50	$177.50
Purchase #4	$64.45	4.228%	$67.1749	$67.17	$67.15	$67.20
Purchase #5	$117.62	9.478%	$128.768	$128.77	$128.75	$128.80
Purchase #6	$242.40	5.836%	$256.5465	$256.55	$256.55	$256.50
Purchase #7	$78.38	13.554%	$89.0036	$89.00	$89.00	$89.00
7 purchase totals =	$809.80		$882.0162	$882.02	$882.00	$882.10