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	$89.38	7.778%	$96.332	$96.33	$96.35	$96.30
Purchase #2	$39.95	13.669%	$45.4108	$45.41	$45.40	$45.40
Purchase #3	$93.79	6.247%	$99.6491	$99.65	$99.65	$99.60
Purchase #4	$83.40	6.505%	$88.8252	$88.83	$88.85	$88.80
Purchase #5	$167.46	8.469%	$181.6422	$181.64	$181.65	$181.60
Purchase #6	$103.96	7.190%	$111.4347	$111.43	$111.45	$111.40
Purchase #7	$192.60	8.293%	$208.5723	$208.57	$208.55	$208.60
7 purchase totals =	$770.54		$831.8663	$831.86	$831.90	$831.70