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	$53.36	5.747%	$56.4266	$56.43	$56.45	$56.40
Purchase #2	$72.30	4.541%	$75.5831	$75.58	$75.60	$75.60
Purchase #3	$202.50	9.697%	$222.1364	$222.14	$222.15	$222.10
Purchase #4	$39.46	7.147%	$42.2802	$42.28	$42.30	$42.30
Purchase #5	$238.73	12.749%	$269.1657	$269.17	$269.15	$269.20
Purchase #6	$87.95	3.331%	$90.8796	$90.88	$90.90	$90.90
Purchase #7	$243.25	9.354%	$266.0036	$266.00	$266.00	$266.00
7 purchase totals =	$937.55		$1,022.4752	$1,022.48	$1,022.55	$1,022.50