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	$191.67	10.248%	$211.3123	$211.31	$211.30	$211.30
Purchase #2	$84.38	5.713%	$89.2006	$89.20	$89.20	$89.20
Purchase #3	$33.74	11.127%	$37.4942	$37.49	$37.50	$37.50
Purchase #4	$129.99	9.525%	$142.3715	$142.37	$142.35	$142.40
Purchase #5	$106.82	5.405%	$112.5936	$112.59	$112.60	$112.60
Purchase #6	$227.73	10.587%	$251.8398	$251.84	$251.85	$251.80
Purchase #7	$214.97	5.384%	$226.544	$226.54	$226.55	$226.50
7 purchase totals =	$989.30		$1,071.3560	$1,071.34	$1,071.35	$1,071.30