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	$140.90	10.461%	$155.6395	$155.64	$155.65	$155.60
Purchase #2	$152.83	3.300%	$157.8734	$157.87	$157.85	$157.90
Purchase #3	$147.76	10.276%	$162.9438	$162.94	$162.95	$162.90
Purchase #4	$130.39	13.193%	$147.5924	$147.59	$147.60	$147.60
Purchase #5	$40.56	11.112%	$45.067	$45.07	$45.05	$45.10
Purchase #6	$204.75	3.458%	$211.8303	$211.83	$211.85	$211.80
Purchase #7	$124.25	3.343%	$128.4037	$128.40	$128.40	$128.40
7 purchase totals =	$941.44		$1,009.3501	$1,009.34	$1,009.35	$1,009.30