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	$218.88	6.586%	$233.2954	$233.30	$233.30	$233.30
Purchase #2	$82.67	13.570%	$93.8883	$93.89	$93.90	$93.90
Purchase #3	$124.64	9.155%	$136.0508	$136.05	$136.05	$136.10
Purchase #4	$83.85	11.283%	$93.3108	$93.31	$93.30	$93.30
Purchase #5	$239.63	6.717%	$255.7259	$255.73	$255.75	$255.70
Purchase #6	$199.59	9.155%	$217.8625	$217.86	$217.85	$217.90
Purchase #7	$126.89	12.602%	$142.8807	$142.88	$142.90	$142.90
7 purchase totals =	$1,076.15		$1,173.0144	$1,173.02	$1,173.05	$1,173.10