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	$56.82	4.519%	$59.3877	$59.39	$59.40	$59.40
Purchase #2	$111.31	6.549%	$118.5997	$118.60	$118.60	$118.60
Purchase #3	$235.69	3.488%	$243.9109	$243.91	$243.90	$243.90
Purchase #4	$121.83	4.313%	$127.0845	$127.08	$127.10	$127.10
Purchase #5	$61.33	4.710%	$64.2186	$64.22	$64.20	$64.20
Purchase #6	$143.73	10.436%	$158.7297	$158.73	$158.75	$158.70
Purchase #7	$168.29	12.621%	$189.5299	$189.53	$189.55	$189.50
7 purchase totals =	$899.00		$961.4610	$961.46	$961.50	$961.40