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	$156.28	5.328%	$164.6066	$164.61	$164.60	$164.60
Purchase #2	$150.59	9.532%	$164.9442	$164.94	$164.95	$164.90
Purchase #3	$15.61	7.138%	$16.7242	$16.72	$16.70	$16.70
Purchase #4	$211.39	12.719%	$238.2767	$238.28	$238.30	$238.30
Purchase #5	$226.89	8.158%	$245.3997	$245.40	$245.40	$245.40
Purchase #6	$19.64	4.443%	$20.5126	$20.51	$20.50	$20.50
Purchase #7	$212.82	13.763%	$242.1104	$242.11	$242.10	$242.10
7 purchase totals =	$993.22		$1,092.5744	$1,092.57	$1,092.55	$1,092.50