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	$53.89	13.429%	$61.1269	$61.13	$61.15	$61.10
Purchase #2	$89.51	11.164%	$99.5029	$99.50	$99.50	$99.50
Purchase #3	$238.55	11.246%	$265.3773	$265.38	$265.40	$265.40
Purchase #4	$246.59	3.825%	$256.0221	$256.02	$256.00	$256.00
Purchase #5	$233.56	11.863%	$261.2672	$261.27	$261.25	$261.30
Purchase #6	$189.50	4.828%	$198.6491	$198.65	$198.65	$198.60
Purchase #7	$49.82	13.728%	$56.6593	$56.66	$56.65	$56.70
7 purchase totals =	$1,101.42		$1,198.6048	$1,198.61	$1,198.60	$1,198.60