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	$146.57	12.756%	$165.2665	$165.27	$165.25	$165.30
Purchase #2	$36.72	3.769%	$38.104	$38.10	$38.10	$38.10
Purchase #3	$143.78	8.541%	$156.0602	$156.06	$156.05	$156.10
Purchase #4	$233.67	5.767%	$247.1457	$247.15	$247.15	$247.10
Purchase #5	$161.54	5.152%	$169.8625	$169.86	$169.85	$169.90
Purchase #6	$162.83	12.469%	$183.1333	$183.13	$183.15	$183.10
Purchase #7	$19.55	11.790%	$21.8549	$21.85	$21.85	$21.90
7 purchase totals =	$904.66		$981.4271	$981.42	$981.40	$981.50