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	$209.98	13.372%	$238.0585	$238.06	$238.05	$238.10
Purchase #2	$54.99	8.220%	$59.5102	$59.51	$59.50	$59.50
Purchase #3	$235.69	3.140%	$243.0907	$243.09	$243.10	$243.10
Purchase #4	$135.90	6.427%	$144.6343	$144.63	$144.65	$144.60
Purchase #5	$80.49	12.453%	$90.5134	$90.51	$90.50	$90.50
Purchase #6	$51.65	6.648%	$55.0837	$55.08	$55.10	$55.10
Purchase #7	$30.82	10.747%	$34.1322	$34.13	$34.15	$34.10
7 purchase totals =	$799.52		$865.0230	$865.01	$865.05	$865.00