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	$206.45	13.473%	$234.265	$234.27	$234.25	$234.30
Purchase #2	$50.84	13.233%	$57.5677	$57.57	$57.55	$57.60
Purchase #3	$168.96	9.140%	$184.4029	$184.40	$184.40	$184.40
Purchase #4	$68.57	5.112%	$72.0753	$72.08	$72.10	$72.10
Purchase #5	$234.34	12.142%	$262.7936	$262.79	$262.80	$262.80
Purchase #6	$73.85	11.581%	$82.4026	$82.40	$82.40	$82.40
Purchase #7	$48.29	13.119%	$54.6252	$54.63	$54.65	$54.60
7 purchase totals =	$851.30		$948.1323	$948.14	$948.15	$948.20