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	$58.40	4.237%	$60.8744	$60.87	$60.85	$60.90
Purchase #2	$153.73	9.468%	$168.2852	$168.29	$168.30	$168.30
Purchase #3	$85.71	3.171%	$88.4279	$88.43	$88.45	$88.40
Purchase #4	$134.79	12.625%	$151.8072	$151.81	$151.80	$151.80
Purchase #5	$68.52	12.776%	$77.2741	$77.27	$77.25	$77.30
Purchase #6	$56.51	4.593%	$59.1055	$59.11	$59.10	$59.10
Purchase #7	$59.40	7.481%	$63.8437	$63.84	$63.85	$63.80
7 purchase totals =	$617.06		$669.6180	$669.62	$669.60	$669.60