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	$166.94	5.692%	$176.4422	$176.44	$176.45	$176.40
Purchase #2	$220.90	7.459%	$237.3769	$237.38	$237.40	$237.40
Purchase #3	$202.53	11.823%	$226.4751	$226.48	$226.50	$226.50
Purchase #4	$46.76	4.549%	$48.8871	$48.89	$48.90	$48.90
Purchase #5	$99.39	9.746%	$109.0765	$109.08	$109.10	$109.10
Purchase #6	$30.47	5.281%	$32.0791	$32.08	$32.10	$32.10
Purchase #7	$110.60	11.650%	$123.4849	$123.48	$123.50	$123.50
7 purchase totals =	$877.59		$953.8218	$953.83	$953.95	$953.90