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	$78.86	4.871%	$82.7013	$82.70	$82.70	$82.70
Purchase #2	$246.38	7.560%	$265.0063	$265.01	$265.00	$265.00
Purchase #3	$146.51	3.743%	$151.9939	$151.99	$152.00	$152.00
Purchase #4	$18.50	7.541%	$19.8951	$19.90	$19.90	$19.90
Purchase #5	$222.32	5.204%	$233.8895	$233.89	$233.90	$233.90
Purchase #6	$144.42	10.270%	$159.2519	$159.25	$159.25	$159.30
Purchase #7	$218.76	11.440%	$243.7861	$243.79	$243.80	$243.80
7 purchase totals =	$1,075.75		$1,156.5241	$1,156.53	$1,156.55	$1,156.60