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	$188.75	6.392%	$200.8149	$200.81	$200.80	$200.80
Purchase #2	$25.71	7.209%	$27.5634	$27.56	$27.55	$27.60
Purchase #3	$192.55	3.354%	$199.0081	$199.01	$199.00	$199.00
Purchase #4	$227.72	3.629%	$235.984	$235.98	$236.00	$236.00
Purchase #5	$227.86	8.799%	$247.9094	$247.91	$247.90	$247.90
Purchase #6	$158.67	6.863%	$169.5595	$169.56	$169.55	$169.60
Purchase #7	$223.59	4.345%	$233.305	$233.31	$233.30	$233.30
7 purchase totals =	$1,244.85		$1,314.1443	$1,314.14	$1,314.10	$1,314.20