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	$106.61	12.173%	$119.5876	$119.59	$119.60	$119.60
Purchase #2	$104.99	13.854%	$119.5353	$119.54	$119.55	$119.50
Purchase #3	$90.30	5.787%	$95.5257	$95.53	$95.55	$95.50
Purchase #4	$201.74	5.292%	$212.4161	$212.42	$212.40	$212.40
Purchase #5	$249.48	11.779%	$278.8662	$278.87	$278.85	$278.90
Purchase #6	$130.64	13.717%	$148.5599	$148.56	$148.55	$148.60
Purchase #7	$123.59	3.784%	$128.2666	$128.27	$128.25	$128.30
7 purchase totals =	$1,007.35		$1,102.7574	$1,102.78	$1,102.75	$1,102.80