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	$188.65	12.591%	$212.4029	$212.40	$212.40	$212.40
Purchase #2	$175.26	4.406%	$182.982	$182.98	$183.00	$183.00
Purchase #3	$143.65	6.147%	$152.4802	$152.48	$152.50	$152.50
Purchase #4	$37.86	13.236%	$42.8711	$42.87	$42.85	$42.90
Purchase #5	$177.31	4.815%	$185.8475	$185.85	$185.85	$185.80
Purchase #6	$151.93	3.278%	$156.9103	$156.91	$156.90	$156.90
Purchase #7	$95.26	9.341%	$104.1582	$104.16	$104.15	$104.20
7 purchase totals =	$969.92		$1,037.6522	$1,037.65	$1,037.65	$1,037.70