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	$169.97	6.772%	$181.4804	$181.48	$181.50	$181.50
Purchase #2	$204.30	11.159%	$227.0978	$227.10	$227.10	$227.10
Purchase #3	$65.78	9.153%	$71.8008	$71.80	$71.80	$71.80
Purchase #4	$73.54	7.293%	$78.9033	$78.90	$78.90	$78.90
Purchase #5	$48.97	13.161%	$55.4149	$55.41	$55.40	$55.40
Purchase #6	$6.68	3.169%	$6.8917	$6.89	$6.90	$6.90
Purchase #7	$73.66	4.743%	$77.1537	$77.15	$77.15	$77.20
7 purchase totals =	$642.90		$698.7426	$698.73	$698.75	$698.80