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	$135.98	11.808%	$152.0365	$152.04	$152.05	$152.00
Purchase #2	$157.90	9.438%	$172.8026	$172.80	$172.80	$172.80
Purchase #3	$245.36	8.212%	$265.509	$265.51	$265.50	$265.50
Purchase #4	$234.65	8.163%	$253.8045	$253.80	$253.80	$253.80
Purchase #5	$129.25	8.623%	$140.3952	$140.40	$140.40	$140.40
Purchase #6	$91.61	11.769%	$102.3916	$102.39	$102.40	$102.40
Purchase #7	$37.79	7.168%	$40.4988	$40.50	$40.50	$40.50
7 purchase totals =	$1,032.54		$1,127.4382	$1,127.44	$1,127.45	$1,127.40