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	$116.40	6.160%	$123.5702	$123.57	$123.55	$123.60
Purchase #2	$142.94	3.751%	$148.3017	$148.30	$148.30	$148.30
Purchase #3	$105.76	6.515%	$112.6503	$112.65	$112.65	$112.70
Purchase #4	$81.90	6.191%	$86.9704	$86.97	$86.95	$87.00
Purchase #5	$222.94	7.467%	$239.5869	$239.59	$239.60	$239.60
Purchase #6	$150.87	11.369%	$168.0224	$168.02	$168.00	$168.00
Purchase #7	$232.77	4.765%	$243.8615	$243.86	$243.85	$243.90
7 purchase totals =	$1,053.58		$1,122.9634	$1,122.96	$1,122.90	$1,123.10