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	$132.55	11.593%	$147.9165	$147.92	$147.90	$147.90
Purchase #2	$234.42	5.176%	$246.5536	$246.55	$246.55	$246.60
Purchase #3	$212.45	9.705%	$233.0683	$233.07	$233.05	$233.10
Purchase #4	$98.86	9.124%	$107.88	$107.88	$107.90	$107.90
Purchase #5	$81.76	11.165%	$90.8885	$90.89	$90.90	$90.90
Purchase #6	$78.41	9.610%	$85.9452	$85.95	$85.95	$85.90
Purchase #7	$96.56	9.596%	$105.8259	$105.83	$105.85	$105.80
7 purchase totals =	$935.01		$1,018.0780	$1,018.09	$1,018.10	$1,018.10