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	$102.51	7.181%	$109.8712	$109.87	$109.85	$109.90
Purchase #2	$54.39	4.540%	$56.8593	$56.86	$56.85	$56.90
Purchase #3	$151.28	8.783%	$164.5669	$164.57	$164.55	$164.60
Purchase #4	$96.35	7.415%	$103.4944	$103.49	$103.50	$103.50
Purchase #5	$224.46	3.849%	$233.0995	$233.10	$233.10	$233.10
Purchase #6	$242.98	11.295%	$270.4246	$270.42	$270.40	$270.40
Purchase #7	$248.68	10.662%	$275.1943	$275.19	$275.20	$275.20
7 purchase totals =	$1,120.65		$1,213.5102	$1,213.50	$1,213.45	$1,213.60