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	$172.71	12.849%	$194.9015	$194.90	$194.90	$194.90
Purchase #2	$207.59	5.104%	$218.1854	$218.19	$218.20	$218.20
Purchase #3	$116.84	13.304%	$132.3844	$132.38	$132.40	$132.40
Purchase #4	$15.33	13.817%	$17.4481	$17.45	$17.45	$17.40
Purchase #5	$39.65	12.230%	$44.4992	$44.50	$44.50	$44.50
Purchase #6	$67.76	6.512%	$72.1725	$72.17	$72.15	$72.20
Purchase #7	$84.95	5.409%	$89.5449	$89.54	$89.55	$89.50
7 purchase totals =	$704.83		$769.1360	$769.13	$769.15	$769.10