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	$48.94	10.214%	$53.9387	$53.94	$53.95	$53.90
Purchase #2	$88.48	5.441%	$93.2942	$93.29	$93.30	$93.30
Purchase #3	$235.82	6.610%	$251.4077	$251.41	$251.40	$251.40
Purchase #4	$136.41	12.211%	$153.067	$153.07	$153.05	$153.10
Purchase #5	$196.27	13.557%	$222.8783	$222.88	$222.90	$222.90
Purchase #6	$182.77	10.864%	$202.6261	$202.63	$202.65	$202.60
Purchase #7	$115.49	6.652%	$123.1724	$123.17	$123.15	$123.20
7 purchase totals =	$1,004.18		$1,100.3844	$1,100.39	$1,100.40	$1,100.40