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	$156.89	3.686%	$162.673	$162.67	$162.65	$162.70
Purchase #2	$132.39	7.705%	$142.5906	$142.59	$142.60	$142.60
Purchase #3	$238.44	8.337%	$258.3187	$258.32	$258.30	$258.30
Purchase #4	$116.78	9.208%	$127.5331	$127.53	$127.55	$127.50
Purchase #5	$57.65	6.424%	$61.3534	$61.35	$61.35	$61.40
Purchase #6	$179.44	6.222%	$190.6048	$190.60	$190.60	$190.60
Purchase #7	$208.60	11.234%	$232.0341	$232.03	$232.05	$232.00
7 purchase totals =	$1,090.19		$1,175.1077	$1,175.09	$1,175.10	$1,175.10