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	$225.52	4.363%	$235.3594	$235.36	$235.35	$235.40
Purchase #2	$46.33	6.673%	$49.4216	$49.42	$49.40	$49.40
Purchase #3	$164.98	5.838%	$174.6115	$174.61	$174.60	$174.60
Purchase #4	$82.29	7.501%	$88.4626	$88.46	$88.45	$88.50
Purchase #5	$171.46	10.805%	$189.9863	$189.99	$190.00	$190.00
Purchase #6	$36.38	12.399%	$40.8908	$40.89	$40.90	$40.90
Purchase #7	$174.96	12.519%	$196.8632	$196.86	$196.85	$196.90
7 purchase totals =	$901.92		$975.5954	$975.59	$975.55	$975.70