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	$149.32	10.188%	$164.5327	$164.53	$164.55	$164.50
Purchase #2	$24.98	11.853%	$27.9409	$27.94	$27.95	$27.90
Purchase #3	$135.28	4.698%	$141.6355	$141.64	$141.65	$141.60
Purchase #4	$75.51	4.303%	$78.7592	$78.76	$78.75	$78.80
Purchase #5	$133.33	12.410%	$149.8763	$149.88	$149.90	$149.90
Purchase #6	$166.88	11.805%	$186.5802	$186.58	$186.60	$186.60
Purchase #7	$65.36	11.502%	$72.8777	$72.88	$72.90	$72.90
7 purchase totals =	$750.66		$822.2025	$822.21	$822.30	$822.20