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	$168.43	10.630%	$186.3341	$186.33	$186.35	$186.30
Purchase #2	$126.90	11.204%	$141.1179	$141.12	$141.10	$141.10
Purchase #3	$117.37	6.468%	$124.9615	$124.96	$124.95	$125.00
Purchase #4	$106.96	4.573%	$111.8513	$111.85	$111.85	$111.90
Purchase #5	$123.50	5.863%	$130.7408	$130.74	$130.75	$130.70
Purchase #6	$176.62	4.770%	$185.0448	$185.04	$185.05	$185.00
Purchase #7	$22.91	10.710%	$25.3637	$25.36	$25.35	$25.40
7 purchase totals =	$842.69		$905.4141	$905.40	$905.40	$905.40