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	$60.72	11.603%	$67.7653	$67.77	$67.75	$67.80
Purchase #2	$75.91	6.147%	$80.5762	$80.58	$80.60	$80.60
Purchase #3	$194.30	7.665%	$209.1931	$209.19	$209.20	$209.20
Purchase #4	$162.32	5.275%	$170.8824	$170.88	$170.90	$170.90
Purchase #5	$168.34	7.860%	$181.5715	$181.57	$181.55	$181.60
Purchase #6	$134.36	6.783%	$143.4736	$143.47	$143.45	$143.50
Purchase #7	$108.76	13.167%	$123.0804	$123.08	$123.10	$123.10
7 purchase totals =	$904.71		$976.5425	$976.54	$976.55	$976.70