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	$128.86	7.171%	$138.1006	$138.10	$138.10	$138.10
Purchase #2	$196.78	9.545%	$215.5627	$215.56	$215.55	$215.60
Purchase #3	$249.43	10.596%	$275.8596	$275.86	$275.85	$275.90
Purchase #4	$178.43	5.384%	$188.0367	$188.04	$188.05	$188.00
Purchase #5	$57.91	9.816%	$63.5944	$63.59	$63.60	$63.60
Purchase #6	$76.36	5.323%	$80.4246	$80.42	$80.40	$80.40
Purchase #7	$143.86	6.187%	$152.7606	$152.76	$152.75	$152.80
7 purchase totals =	$1,031.63		$1,114.3392	$1,114.33	$1,114.30	$1,114.40