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	$182.91	8.543%	$198.536	$198.54	$198.55	$198.50
Purchase #2	$112.34	3.832%	$116.6449	$116.64	$116.65	$116.60
Purchase #3	$95.95	8.151%	$103.7709	$103.77	$103.75	$103.80
Purchase #4	$238.29	4.711%	$249.5158	$249.52	$249.50	$249.50
Purchase #5	$200.86	8.739%	$218.4132	$218.41	$218.40	$218.40
Purchase #6	$52.34	10.637%	$57.9074	$57.91	$57.90	$57.90
Purchase #7	$53.25	6.830%	$56.887	$56.89	$56.90	$56.90
7 purchase totals =	$935.94		$1,001.6752	$1,001.68	$1,001.65	$1,001.60