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	$142.73	9.150%	$155.7898	$155.79	$155.80	$155.80
Purchase #2	$159.75	13.483%	$181.2891	$181.29	$181.30	$181.30
Purchase #3	$173.44	7.682%	$186.7637	$186.76	$186.75	$186.80
Purchase #4	$133.94	12.861%	$151.166	$151.17	$151.15	$151.20
Purchase #5	$100.85	5.654%	$106.5521	$106.55	$106.55	$106.60
Purchase #6	$57.32	9.134%	$62.5556	$62.56	$62.55	$62.60
Purchase #7	$108.75	13.420%	$123.3443	$123.34	$123.35	$123.30
7 purchase totals =	$876.78		$967.4606	$967.46	$967.45	$967.60