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	$220.36	13.557%	$250.2342	$250.23	$250.25	$250.20
Purchase #2	$188.66	13.499%	$214.1272	$214.13	$214.15	$214.10
Purchase #3	$53.96	9.539%	$59.1072	$59.11	$59.10	$59.10
Purchase #4	$86.66	3.477%	$89.6732	$89.67	$89.65	$89.70
Purchase #5	$237.86	5.798%	$251.6511	$251.65	$251.65	$251.70
Purchase #6	$11.85	10.526%	$13.0973	$13.10	$13.10	$13.10
Purchase #7	$139.89	3.400%	$144.6463	$144.65	$144.65	$144.60
7 purchase totals =	$939.24		$1,022.5365	$1,022.54	$1,022.55	$1,022.50