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	$133.30	12.351%	$149.7639	$149.76	$149.75	$149.80
Purchase #2	$112.94	9.576%	$123.7551	$123.76	$123.75	$123.80
Purchase #3	$154.94	11.347%	$172.521	$172.52	$172.50	$172.50
Purchase #4	$27.27	11.121%	$30.3027	$30.30	$30.30	$30.30
Purchase #5	$243.52	9.180%	$265.8751	$265.88	$265.90	$265.90
Purchase #6	$131.48	8.461%	$142.6045	$142.60	$142.60	$142.60
Purchase #7	$212.72	4.450%	$222.186	$222.19	$222.20	$222.20
7 purchase totals =	$1,016.17		$1,107.0083	$1,107.01	$1,107.00	$1,107.10