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	$189.25	3.128%	$195.1697	$195.17	$195.15	$195.20
Purchase #2	$99.71	13.558%	$113.2287	$113.23	$113.25	$113.20
Purchase #3	$144.54	9.207%	$157.8478	$157.85	$157.85	$157.80
Purchase #4	$164.57	9.173%	$179.666	$179.67	$179.65	$179.70
Purchase #5	$89.55	13.443%	$101.5882	$101.59	$101.60	$101.60
Purchase #6	$222.37	12.374%	$249.8861	$249.89	$249.90	$249.90
Purchase #7	$39.41	13.749%	$44.8285	$44.83	$44.85	$44.80
7 purchase totals =	$949.40		$1,042.2150	$1,042.23	$1,042.25	$1,042.20