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	$145.76	10.230%	$160.6712	$160.67	$160.65	$160.70
Purchase #2	$228.39	6.744%	$243.7926	$243.79	$243.80	$243.80
Purchase #3	$190.43	13.439%	$216.0219	$216.02	$216.00	$216.00
Purchase #4	$188.55	7.350%	$202.4084	$202.41	$202.40	$202.40
Purchase #5	$40.80	12.462%	$45.8845	$45.88	$45.90	$45.90
Purchase #6	$158.90	8.647%	$172.6401	$172.64	$172.65	$172.60
Purchase #7	$63.39	11.330%	$70.5721	$70.57	$70.55	$70.60
7 purchase totals =	$1,016.22		$1,111.9908	$1,111.98	$1,111.95	$1,112.00