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	$94.71	11.322%	$105.4331	$105.43	$105.45	$105.40
Purchase #2	$225.89	13.810%	$257.0854	$257.09	$257.10	$257.10
Purchase #3	$242.49	3.677%	$251.4064	$251.41	$251.40	$251.40
Purchase #4	$84.34	9.539%	$92.3852	$92.39	$92.40	$92.40
Purchase #5	$86.85	5.804%	$91.8908	$91.89	$91.90	$91.90
Purchase #6	$230.53	3.372%	$238.3035	$238.30	$238.30	$238.30
Purchase #7	$86.76	10.185%	$95.5965	$95.60	$95.60	$95.60
7 purchase totals =	$1,051.57		$1,132.1009	$1,132.11	$1,132.15	$1,132.10