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	$80.82	10.452%	$89.2673	$89.27	$89.25	$89.30
Purchase #2	$177.50	7.761%	$191.2758	$191.28	$191.30	$191.30
Purchase #3	$205.27	9.827%	$225.4419	$225.44	$225.45	$225.40
Purchase #4	$180.93	3.168%	$186.6619	$186.66	$186.65	$186.70
Purchase #5	$95.79	11.379%	$106.6899	$106.69	$106.70	$106.70
Purchase #6	$36.96	5.343%	$38.9348	$38.93	$38.95	$38.90
Purchase #7	$223.77	6.337%	$237.9503	$237.95	$237.95	$238.00
7 purchase totals =	$1,001.04		$1,076.2219	$1,076.22	$1,076.25	$1,076.30