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	$29.90	8.752%	$32.5168	$32.52	$32.50	$32.50
Purchase #2	$162.46	13.423%	$184.267	$184.27	$184.25	$184.30
Purchase #3	$40.37	5.668%	$42.6582	$42.66	$42.65	$42.70
Purchase #4	$171.33	10.537%	$189.383	$189.38	$189.40	$189.40
Purchase #5	$205.75	12.456%	$231.3782	$231.38	$231.40	$231.40
Purchase #6	$181.71	5.723%	$192.1093	$192.11	$192.10	$192.10
Purchase #7	$212.58	8.833%	$231.3572	$231.36	$231.35	$231.40
7 purchase totals =	$1,004.10		$1,103.6697	$1,103.68	$1,103.65	$1,103.80