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	$50.38	11.225%	$56.0352	$56.04	$56.05	$56.00
Purchase #2	$192.95	8.192%	$208.7565	$208.76	$208.75	$208.80
Purchase #3	$99.33	7.233%	$106.5145	$106.51	$106.50	$106.50
Purchase #4	$144.45	12.422%	$162.3936	$162.39	$162.40	$162.40
Purchase #5	$65.93	10.107%	$72.5935	$72.59	$72.60	$72.60
Purchase #6	$246.51	9.608%	$270.1947	$270.19	$270.20	$270.20
Purchase #7	$121.91	7.449%	$130.9911	$130.99	$131.00	$131.00
7 purchase totals =	$921.46		$1,007.4791	$1,007.47	$1,007.50	$1,007.50