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	$54.32	7.765%	$58.5379	$58.54	$58.55	$58.50
Purchase #2	$175.35	7.599%	$188.6748	$188.67	$188.65	$188.70
Purchase #3	$173.52	5.735%	$183.4714	$183.47	$183.45	$183.50
Purchase #4	$111.84	12.250%	$125.5404	$125.54	$125.55	$125.50
Purchase #5	$77.42	6.667%	$82.5816	$82.58	$82.60	$82.60
Purchase #6	$30.90	3.781%	$32.0683	$32.07	$32.05	$32.10
Purchase #7	$230.96	13.116%	$261.2527	$261.25	$261.25	$261.30
7 purchase totals =	$854.31		$932.1271	$932.12	$932.10	$932.20