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	$42.65	3.414%	$44.1061	$44.11	$44.10	$44.10
Purchase #2	$53.26	13.334%	$60.3617	$60.36	$60.35	$60.40
Purchase #3	$218.52	4.247%	$227.8005	$227.80	$227.80	$227.80
Purchase #4	$140.69	10.584%	$155.5806	$155.58	$155.60	$155.60
Purchase #5	$62.76	8.214%	$67.9151	$67.92	$67.90	$67.90
Purchase #6	$85.76	5.815%	$90.7469	$90.75	$90.75	$90.70
Purchase #7	$37.45	10.557%	$41.4036	$41.40	$41.40	$41.40
7 purchase totals =	$641.09		$687.9145	$687.92	$687.90	$687.90