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	$80.56	10.146%	$88.7336	$88.73	$88.75	$88.70
Purchase #2	$14.47	7.479%	$15.5522	$15.55	$15.55	$15.60
Purchase #3	$109.94	4.183%	$114.5388	$114.54	$114.55	$114.50
Purchase #4	$25.89	6.137%	$27.4789	$27.48	$27.50	$27.50
Purchase #5	$182.41	4.298%	$190.25	$190.25	$190.25	$190.30
Purchase #6	$51.39	6.616%	$54.79	$54.79	$54.80	$54.80
Purchase #7	$244.95	5.288%	$257.903	$257.90	$257.90	$257.90
7 purchase totals =	$709.61		$749.2465	$749.24	$749.30	$749.30