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	$55.60	12.473%	$62.535	$62.54	$62.55	$62.50
Purchase #2	$247.43	9.156%	$270.0847	$270.08	$270.10	$270.10
Purchase #3	$130.87	11.350%	$145.7237	$145.72	$145.70	$145.70
Purchase #4	$200.39	4.808%	$210.0248	$210.02	$210.00	$210.00
Purchase #5	$227.25	10.696%	$251.5567	$251.56	$251.55	$251.60
Purchase #6	$186.59	5.207%	$196.3057	$196.31	$196.30	$196.30
Purchase #7	$180.48	4.795%	$189.134	$189.13	$189.15	$189.10
7 purchase totals =	$1,228.61		$1,325.3646	$1,325.36	$1,325.35	$1,325.30