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	$126.32	5.387%	$133.1249	$133.12	$133.10	$133.10
Purchase #2	$51.33	4.746%	$53.7661	$53.77	$53.75	$53.80
Purchase #3	$249.51	7.744%	$268.8321	$268.83	$268.85	$268.80
Purchase #4	$13.49	5.269%	$14.2008	$14.20	$14.20	$14.20
Purchase #5	$130.35	7.282%	$139.8421	$139.84	$139.85	$139.80
Purchase #6	$176.63	11.424%	$196.8082	$196.81	$196.80	$196.80
Purchase #7	$249.98	11.430%	$278.5527	$278.55	$278.55	$278.60
7 purchase totals =	$997.61		$1,085.1269	$1,085.12	$1,085.10	$1,085.10