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	$175.75	5.503%	$185.4215	$185.42	$185.40	$185.40
Purchase #2	$207.55	12.788%	$234.0915	$234.09	$234.10	$234.10
Purchase #3	$131.71	6.188%	$139.8602	$139.86	$139.85	$139.90
Purchase #4	$174.59	4.805%	$182.979	$182.98	$183.00	$183.00
Purchase #5	$214.47	11.157%	$238.3984	$238.40	$238.40	$238.40
Purchase #6	$30.54	13.816%	$34.7594	$34.76	$34.75	$34.80
Purchase #7	$57.33	7.357%	$61.5478	$61.55	$61.55	$61.50
7 purchase totals =	$991.94		$1,077.0578	$1,077.06	$1,077.05	$1,077.10