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	$62.49	7.227%	$67.0062	$67.01	$67.00	$67.00
Purchase #2	$152.77	6.249%	$162.3166	$162.32	$162.30	$162.30
Purchase #3	$53.84	12.459%	$60.5479	$60.55	$60.55	$60.50
Purchase #4	$182.29	7.663%	$196.2589	$196.26	$196.25	$196.30
Purchase #5	$78.73	10.713%	$87.1643	$87.16	$87.15	$87.20
Purchase #6	$148.87	13.474%	$168.9287	$168.93	$168.95	$168.90
Purchase #7	$128.78	6.240%	$136.8159	$136.82	$136.80	$136.80
7 purchase totals =	$807.77		$879.0385	$879.05	$879.00	$879.00