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	$238.63	10.361%	$263.3545	$263.35	$263.35	$263.40
Purchase #2	$217.96	3.434%	$225.4447	$225.44	$225.45	$225.40
Purchase #3	$40.98	3.856%	$42.5602	$42.56	$42.55	$42.60
Purchase #4	$222.55	11.689%	$248.5639	$248.56	$248.55	$248.60
Purchase #5	$123.33	6.680%	$131.5684	$131.57	$131.55	$131.60
Purchase #6	$51.59	9.367%	$56.4224	$56.42	$56.40	$56.40
Purchase #7	$184.38	7.655%	$198.4943	$198.49	$198.50	$198.50
7 purchase totals =	$1,079.42		$1,166.4084	$1,166.39	$1,166.35	$1,166.50