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	$200.41	4.435%	$209.2982	$209.30	$209.30	$209.30
Purchase #2	$36.41	11.491%	$40.5939	$40.59	$40.60	$40.60
Purchase #3	$195.56	7.688%	$210.5947	$210.59	$210.60	$210.60
Purchase #4	$212.96	9.425%	$233.0315	$233.03	$233.05	$233.00
Purchase #5	$72.98	7.705%	$78.6031	$78.60	$78.60	$78.60
Purchase #6	$217.64	10.756%	$241.0494	$241.05	$241.05	$241.00
Purchase #7	$14.88	9.529%	$16.2979	$16.30	$16.30	$16.30
7 purchase totals =	$950.84		$1,029.4687	$1,029.46	$1,029.50	$1,029.40