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	$67.86	4.676%	$71.0331	$71.03	$71.05	$71.00
Purchase #2	$167.59	11.287%	$186.5059	$186.51	$186.50	$186.50
Purchase #3	$82.32	3.789%	$85.4391	$85.44	$85.45	$85.40
Purchase #4	$186.25	9.598%	$204.1263	$204.13	$204.15	$204.10
Purchase #5	$220.48	10.693%	$244.0559	$244.06	$244.05	$244.10
Purchase #6	$146.42	3.742%	$151.899	$151.90	$151.90	$151.90
Purchase #7	$126.97	5.342%	$133.7527	$133.75	$133.75	$133.80
7 purchase totals =	$997.89		$1,076.8120	$1,076.82	$1,076.85	$1,076.80