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	$223.26	10.258%	$246.162	$246.16	$246.15	$246.20
Purchase #2	$37.35	12.528%	$42.0292	$42.03	$42.05	$42.00
Purchase #3	$213.86	6.561%	$227.8914	$227.89	$227.90	$227.90
Purchase #4	$46.95	3.573%	$48.6275	$48.63	$48.65	$48.60
Purchase #5	$172.48	8.330%	$186.8476	$186.85	$186.85	$186.80
Purchase #6	$210.88	9.773%	$231.4893	$231.49	$231.50	$231.50
Purchase #7	$89.52	8.204%	$96.8642	$96.86	$96.85	$96.90
7 purchase totals =	$994.30		$1,079.9112	$1,079.91	$1,079.95	$1,079.90