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	$193.30	12.683%	$217.8162	$217.82	$217.80	$217.80
Purchase #2	$71.92	12.179%	$80.6791	$80.68	$80.70	$80.70
Purchase #3	$84.48	3.104%	$87.1023	$87.10	$87.10	$87.10
Purchase #4	$100.58	5.210%	$105.8202	$105.82	$105.80	$105.80
Purchase #5	$149.71	10.645%	$165.6466	$165.65	$165.65	$165.60
Purchase #6	$250.68	12.462%	$281.9197	$281.92	$281.90	$281.90
Purchase #7	$35.84	5.710%	$37.8865	$37.89	$37.90	$37.90
7 purchase totals =	$886.51		$976.8706	$976.88	$976.85	$976.80