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	$211.91	10.842%	$234.8853	$234.89	$234.90	$234.90
Purchase #2	$90.63	11.155%	$100.7398	$100.74	$100.75	$100.70
Purchase #3	$153.96	5.550%	$162.5048	$162.50	$162.50	$162.50
Purchase #4	$248.63	8.762%	$270.415	$270.42	$270.40	$270.40
Purchase #5	$166.25	5.184%	$174.8684	$174.87	$174.85	$174.90
Purchase #6	$66.70	10.171%	$73.4841	$73.48	$73.50	$73.50
Purchase #7	$234.84	5.453%	$247.6458	$247.65	$247.65	$247.60
7 purchase totals =	$1,172.92		$1,264.5432	$1,264.55	$1,264.55	$1,264.50