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	$223.56	3.573%	$231.5478	$231.55	$231.55	$231.50
Purchase #2	$195.40	11.445%	$217.7635	$217.76	$217.75	$217.80
Purchase #3	$144.59	8.282%	$156.5649	$156.56	$156.55	$156.60
Purchase #4	$137.36	6.127%	$145.776	$145.78	$145.80	$145.80
Purchase #5	$73.35	6.833%	$78.362	$78.36	$78.35	$78.40
Purchase #6	$83.54	5.747%	$88.341	$88.34	$88.35	$88.30
Purchase #7	$31.61	5.311%	$33.2888	$33.29	$33.30	$33.30
7 purchase totals =	$889.41		$951.6440	$951.64	$951.65	$951.70