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	$173.37	4.869%	$181.8114	$181.81	$181.80	$181.80
Purchase #2	$127.45	10.328%	$140.613	$140.61	$140.60	$140.60
Purchase #3	$73.29	4.294%	$76.4371	$76.44	$76.45	$76.40
Purchase #4	$192.35	12.591%	$216.5688	$216.57	$216.55	$216.60
Purchase #5	$164.31	10.817%	$182.0834	$182.08	$182.10	$182.10
Purchase #6	$105.87	12.309%	$118.9015	$118.90	$118.90	$118.90
Purchase #7	$42.79	7.179%	$45.8619	$45.86	$45.85	$45.90
7 purchase totals =	$879.43		$962.2771	$962.27	$962.25	$962.30