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	$83.82	4.288%	$87.4142	$87.41	$87.40	$87.40
Purchase #2	$152.98	7.212%	$164.0129	$164.01	$164.00	$164.00
Purchase #3	$44.51	7.445%	$47.8238	$47.82	$47.80	$47.80
Purchase #4	$94.33	6.636%	$100.5897	$100.59	$100.60	$100.60
Purchase #5	$183.30	4.450%	$191.4569	$191.46	$191.45	$191.50
Purchase #6	$237.33	5.315%	$249.9441	$249.94	$249.95	$249.90
Purchase #7	$77.27	11.494%	$86.1514	$86.15	$86.15	$86.20
7 purchase totals =	$873.54		$927.3930	$927.38	$927.35	$927.40