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	$59.56	9.709%	$65.3427	$65.34	$65.35	$65.30
Purchase #2	$127.46	11.869%	$142.5882	$142.59	$142.60	$142.60
Purchase #3	$197.48	12.432%	$222.0307	$222.03	$222.05	$222.00
Purchase #4	$76.84	11.226%	$85.4661	$85.47	$85.45	$85.50
Purchase #5	$195.35	11.467%	$217.7508	$217.75	$217.75	$217.80
Purchase #6	$231.54	5.137%	$243.4342	$243.43	$243.45	$243.40
Purchase #7	$220.43	12.261%	$247.4569	$247.46	$247.45	$247.50
7 purchase totals =	$1,108.66		$1,224.0696	$1,224.07	$1,224.10	$1,224.10