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	$50.48	7.560%	$54.2963	$54.30	$54.30	$54.30
Purchase #2	$148.47	4.252%	$154.7829	$154.78	$154.80	$154.80
Purchase #3	$248.95	3.852%	$258.5396	$258.54	$258.55	$258.50
Purchase #4	$222.32	7.292%	$238.5316	$238.53	$238.55	$238.50
Purchase #5	$48.71	9.655%	$53.413	$53.41	$53.40	$53.40
Purchase #6	$249.25	13.219%	$282.1984	$282.20	$282.20	$282.20
Purchase #7	$73.51	7.225%	$78.8211	$78.82	$78.80	$78.80
7 purchase totals =	$1,041.69		$1,120.5829	$1,120.58	$1,120.60	$1,120.50