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	$165.26	11.726%	$184.6384	$184.64	$184.65	$184.60
Purchase #2	$97.42	7.275%	$104.5073	$104.51	$104.50	$104.50
Purchase #3	$135.98	12.713%	$153.2671	$153.27	$153.25	$153.30
Purchase #4	$89.66	6.605%	$95.582	$95.58	$95.60	$95.60
Purchase #5	$24.71	11.107%	$27.4545	$27.45	$27.45	$27.50
Purchase #6	$100.34	9.186%	$109.5572	$109.56	$109.55	$109.60
Purchase #7	$48.84	13.794%	$55.577	$55.58	$55.60	$55.60
7 purchase totals =	$662.21		$730.5835	$730.59	$730.60	$730.70