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	$77.97	5.534%	$82.2849	$82.28	$82.30	$82.30
Purchase #2	$40.70	6.581%	$43.3785	$43.38	$43.40	$43.40
Purchase #3	$101.25	7.615%	$108.9602	$108.96	$108.95	$109.00
Purchase #4	$50.83	12.678%	$57.2742	$57.27	$57.25	$57.30
Purchase #5	$105.52	12.162%	$118.3533	$118.35	$118.35	$118.40
Purchase #6	$92.54	13.366%	$104.9089	$104.91	$104.90	$104.90
Purchase #7	$179.61	3.658%	$186.1801	$186.18	$186.20	$186.20
7 purchase totals =	$648.42		$701.3401	$701.33	$701.35	$701.50