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	$167.61	13.139%	$189.6323	$189.63	$189.65	$189.60
Purchase #2	$198.29	13.417%	$224.8946	$224.89	$224.90	$224.90
Purchase #3	$162.68	13.731%	$185.0176	$185.02	$185.00	$185.00
Purchase #4	$131.45	8.420%	$142.5181	$142.52	$142.50	$142.50
Purchase #5	$144.46	5.802%	$152.8416	$152.84	$152.85	$152.80
Purchase #6	$218.87	12.135%	$245.4299	$245.43	$245.45	$245.40
Purchase #7	$6.48	8.590%	$7.0366	$7.04	$7.05	$7.00
7 purchase totals =	$1,029.84		$1,147.3707	$1,147.37	$1,147.40	$1,147.20