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	$53.46	10.158%	$58.8905	$58.89	$58.90	$58.90
Purchase #2	$211.38	5.702%	$223.4329	$223.43	$223.45	$223.40
Purchase #3	$88.59	10.457%	$97.8539	$97.85	$97.85	$97.90
Purchase #4	$94.85	10.595%	$104.8994	$104.90	$104.90	$104.90
Purchase #5	$93.73	11.117%	$104.15	$104.15	$104.15	$104.20
Purchase #6	$214.92	10.473%	$237.4286	$237.43	$237.45	$237.40
Purchase #7	$210.48	8.112%	$227.5541	$227.55	$227.55	$227.60
7 purchase totals =	$967.41		$1,054.2094	$1,054.20	$1,054.25	$1,054.30