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	$149.33	4.533%	$156.0991	$156.10	$156.10	$156.10
Purchase #2	$89.75	12.299%	$100.7884	$100.79	$100.80	$100.80
Purchase #3	$136.46	4.289%	$142.3128	$142.31	$142.30	$142.30
Purchase #4	$132.38	13.811%	$150.663	$150.66	$150.65	$150.70
Purchase #5	$141.90	3.677%	$147.1177	$147.12	$147.10	$147.10
Purchase #6	$76.89	10.824%	$85.2126	$85.21	$85.20	$85.20
Purchase #7	$224.35	4.335%	$234.0756	$234.08	$234.10	$234.10
7 purchase totals =	$951.06		$1,016.2692	$1,016.27	$1,016.25	$1,016.30