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	$50.93	6.466%	$54.2231	$54.22	$54.20	$54.20
Purchase #2	$235.72	6.460%	$250.9475	$250.95	$250.95	$250.90
Purchase #3	$71.91	6.675%	$76.71	$76.71	$76.70	$76.70
Purchase #4	$171.31	9.287%	$187.2196	$187.22	$187.20	$187.20
Purchase #5	$142.27	7.208%	$152.5248	$152.52	$152.50	$152.50
Purchase #6	$97.48	6.705%	$104.016	$104.02	$104.00	$104.00
Purchase #7	$207.98	11.673%	$232.2575	$232.26	$232.25	$232.30
7 purchase totals =	$977.60		$1,057.8985	$1,057.90	$1,057.80	$1,057.80