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	$213.33	10.461%	$235.6465	$235.65	$235.65	$235.60
Purchase #2	$168.54	12.735%	$190.0036	$190.00	$190.00	$190.00
Purchase #3	$104.49	8.347%	$113.2118	$113.21	$113.20	$113.20
Purchase #4	$151.85	13.493%	$172.3391	$172.34	$172.35	$172.30
Purchase #5	$57.81	6.138%	$61.3584	$61.36	$61.35	$61.40
Purchase #6	$204.35	12.501%	$229.8958	$229.90	$229.90	$229.90
Purchase #7	$46.51	11.836%	$52.0149	$52.01	$52.00	$52.00
7 purchase totals =	$946.88		$1,054.4701	$1,054.47	$1,054.45	$1,054.40