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	$112.84	10.300%	$124.4625	$124.46	$124.45	$124.50
Purchase #2	$6.55	13.117%	$7.4092	$7.41	$7.40	$7.40
Purchase #3	$56.71	4.814%	$59.44	$59.44	$59.45	$59.40
Purchase #4	$103.51	7.794%	$111.5776	$111.58	$111.60	$111.60
Purchase #5	$183.73	10.191%	$202.4539	$202.45	$202.45	$202.50
Purchase #6	$29.32	13.529%	$33.2867	$33.29	$33.30	$33.30
Purchase #7	$152.35	12.116%	$170.8087	$170.81	$170.80	$170.80
7 purchase totals =	$645.01		$709.4386	$709.44	$709.45	$709.50