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	$163.52	3.198%	$168.7494	$168.75	$168.75	$168.70
Purchase #2	$89.48	8.298%	$96.9051	$96.91	$96.90	$96.90
Purchase #3	$52.30	12.527%	$58.8516	$58.85	$58.85	$58.90
Purchase #4	$50.72	3.289%	$52.3882	$52.39	$52.40	$52.40
Purchase #5	$198.29	3.574%	$205.3769	$205.38	$205.40	$205.40
Purchase #6	$79.78	13.614%	$90.6412	$90.64	$90.65	$90.60
Purchase #7	$73.94	3.308%	$76.3859	$76.39	$76.40	$76.40
7 purchase totals =	$708.03		$749.2983	$749.31	$749.35	$749.30