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	$188.40	9.727%	$206.7257	$206.73	$206.75	$206.70
Purchase #2	$200.69	11.567%	$223.9038	$223.90	$223.90	$223.90
Purchase #3	$159.32	3.213%	$164.439	$164.44	$164.45	$164.40
Purchase #4	$75.53	13.349%	$85.6125	$85.61	$85.60	$85.60
Purchase #5	$80.32	10.844%	$89.0299	$89.03	$89.05	$89.00
Purchase #6	$75.46	4.393%	$78.775	$78.78	$78.80	$78.80
Purchase #7	$56.67	6.759%	$60.5003	$60.50	$60.50	$60.50
7 purchase totals =	$836.39		$908.9862	$908.99	$909.05	$908.90