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	$222.54	13.265%	$252.0599	$252.06	$252.05	$252.10
Purchase #2	$99.99	11.605%	$111.5938	$111.59	$111.60	$111.60
Purchase #3	$222.28	4.294%	$231.8247	$231.82	$231.80	$231.80
Purchase #4	$7.66	3.345%	$7.9162	$7.92	$7.90	$7.90
Purchase #5	$36.36	10.264%	$40.092	$40.09	$40.10	$40.10
Purchase #6	$54.37	12.258%	$61.0347	$61.03	$61.05	$61.00
Purchase #7	$197.67	10.566%	$218.5558	$218.56	$218.55	$218.60
7 purchase totals =	$840.87		$923.0771	$923.07	$923.05	$923.10