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	$229.55	8.151%	$248.2606	$248.26	$248.25	$248.30
Purchase #2	$80.73	3.361%	$83.4433	$83.44	$83.45	$83.40
Purchase #3	$168.66	13.155%	$190.8472	$190.85	$190.85	$190.80
Purchase #4	$206.46	10.457%	$228.0495	$228.05	$228.05	$228.00
Purchase #5	$114.96	10.864%	$127.4493	$127.45	$127.45	$127.40
Purchase #6	$196.71	10.508%	$217.3803	$217.38	$217.40	$217.40
Purchase #7	$146.44	13.111%	$165.6397	$165.64	$165.65	$165.60
7 purchase totals =	$1,143.51		$1,261.0699	$1,261.07	$1,261.10	$1,260.90