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	$217.37	9.645%	$238.3353	$238.34	$238.35	$238.30
Purchase #2	$52.75	3.478%	$54.5846	$54.58	$54.60	$54.60
Purchase #3	$218.30	13.132%	$246.9672	$246.97	$246.95	$247.00
Purchase #4	$83.31	11.484%	$92.8773	$92.88	$92.90	$92.90
Purchase #5	$84.42	5.383%	$88.9643	$88.96	$88.95	$89.00
Purchase #6	$188.54	4.140%	$196.3456	$196.35	$196.35	$196.30
Purchase #7	$16.70	10.645%	$18.4777	$18.48	$18.50	$18.50
7 purchase totals =	$861.39		$936.5520	$936.56	$936.60	$936.60