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	$142.81	5.250%	$150.3075	$150.31	$150.30	$150.30
Purchase #2	$30.78	9.685%	$33.761	$33.76	$33.75	$33.80
Purchase #3	$218.61	6.534%	$232.894	$232.89	$232.90	$232.90
Purchase #4	$142.48	11.734%	$159.1986	$159.20	$159.20	$159.20
Purchase #5	$154.39	10.755%	$170.9946	$170.99	$171.00	$171.00
Purchase #6	$187.32	6.476%	$199.4508	$199.45	$199.45	$199.50
Purchase #7	$52.61	6.659%	$56.1133	$56.11	$56.10	$56.10
7 purchase totals =	$929.00		$1,002.7198	$1,002.71	$1,002.70	$1,002.80