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	$201.49	10.788%	$223.2267	$223.23	$223.25	$223.20
Purchase #2	$48.32	5.772%	$51.109	$51.11	$51.10	$51.10
Purchase #3	$32.79	9.165%	$35.7952	$35.80	$35.80	$35.80
Purchase #4	$201.67	11.533%	$224.9286	$224.93	$224.95	$224.90
Purchase #5	$63.95	12.873%	$72.1823	$72.18	$72.20	$72.20
Purchase #6	$202.46	12.527%	$227.8222	$227.82	$227.80	$227.80
Purchase #7	$243.93	8.790%	$265.3714	$265.37	$265.35	$265.40
7 purchase totals =	$994.61		$1,100.4354	$1,100.44	$1,100.45	$1,100.40