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	$81.65	12.256%	$91.657	$91.66	$91.65	$91.70
Purchase #2	$218.63	6.790%	$233.475	$233.48	$233.50	$233.50
Purchase #3	$165.31	8.544%	$179.4341	$179.43	$179.45	$179.40
Purchase #4	$141.53	10.277%	$156.075	$156.08	$156.10	$156.10
Purchase #5	$111.62	13.319%	$126.4867	$126.49	$126.50	$126.50
Purchase #6	$99.76	7.741%	$107.4824	$107.48	$107.50	$107.50
Purchase #7	$180.70	3.384%	$186.8149	$186.81	$186.80	$186.80
7 purchase totals =	$999.20		$1,081.4251	$1,081.43	$1,081.50	$1,081.50