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	$196.43	13.349%	$222.6514	$222.65	$222.65	$222.70
Purchase #2	$183.28	9.571%	$200.8217	$200.82	$200.80	$200.80
Purchase #3	$66.27	7.170%	$71.0216	$71.02	$71.00	$71.00
Purchase #4	$100.49	7.622%	$108.1493	$108.15	$108.15	$108.10
Purchase #5	$171.64	8.631%	$186.4542	$186.45	$186.45	$186.50
Purchase #6	$147.75	10.140%	$162.7319	$162.73	$162.75	$162.70
Purchase #7	$30.27	3.853%	$31.4363	$31.44	$31.45	$31.40
7 purchase totals =	$896.13		$983.2664	$983.26	$983.25	$983.20