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	$186.27	7.653%	$200.5252	$200.53	$200.55	$200.50
Purchase #2	$203.25	11.718%	$227.0668	$227.07	$227.05	$227.10
Purchase #3	$146.67	5.792%	$155.1651	$155.17	$155.15	$155.20
Purchase #4	$181.57	3.828%	$188.5205	$188.52	$188.50	$188.50
Purchase #5	$73.76	3.729%	$76.5105	$76.51	$76.50	$76.50
Purchase #6	$245.50	10.341%	$270.8872	$270.89	$270.90	$270.90
Purchase #7	$38.38	7.661%	$41.3203	$41.32	$41.30	$41.30
7 purchase totals =	$1,075.40		$1,159.9956	$1,160.01	$1,159.95	$1,160.00