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	$72.51	4.658%	$75.8875	$75.89	$75.90	$75.90
Purchase #2	$64.56	4.466%	$67.4432	$67.44	$67.45	$67.40
Purchase #3	$41.88	4.614%	$43.8123	$43.81	$43.80	$43.80
Purchase #4	$104.84	13.451%	$118.942	$118.94	$118.95	$118.90
Purchase #5	$26.82	7.866%	$28.9297	$28.93	$28.95	$28.90
Purchase #6	$206.58	12.676%	$232.7661	$232.77	$232.75	$232.80
Purchase #7	$204.59	6.805%	$218.5123	$218.51	$218.50	$218.50
7 purchase totals =	$721.78		$786.2931	$786.29	$786.30	$786.20