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	$89.84	7.776%	$96.826	$96.83	$96.85	$96.80
Purchase #2	$89.54	5.605%	$94.5587	$94.56	$94.55	$94.60
Purchase #3	$154.58	6.312%	$164.3371	$164.34	$164.35	$164.30
Purchase #4	$113.85	8.610%	$123.6525	$123.65	$123.65	$123.70
Purchase #5	$202.86	10.357%	$223.8702	$223.87	$223.85	$223.90
Purchase #6	$240.72	10.304%	$265.5238	$265.52	$265.50	$265.50
Purchase #7	$65.28	9.631%	$71.5671	$71.57	$71.55	$71.60
7 purchase totals =	$956.67		$1,040.3354	$1,040.34	$1,040.30	$1,040.40