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	$210.49	12.504%	$236.8097	$236.81	$236.80	$236.80
Purchase #2	$248.27	6.319%	$263.9582	$263.96	$263.95	$264.00
Purchase #3	$133.71	13.155%	$151.2996	$151.30	$151.30	$151.30
Purchase #4	$128.76	8.264%	$139.4007	$139.40	$139.40	$139.40
Purchase #5	$131.76	7.448%	$141.5735	$141.57	$141.55	$141.60
Purchase #6	$59.49	3.493%	$61.568	$61.57	$61.55	$61.60
Purchase #7	$57.29	7.478%	$61.5741	$61.57	$61.55	$61.60
7 purchase totals =	$969.77		$1,056.1838	$1,056.18	$1,056.10	$1,056.30