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	$64.56	11.307%	$71.8598	$71.86	$71.85	$71.90
Purchase #2	$120.86	5.184%	$127.1254	$127.13	$127.15	$127.10
Purchase #3	$242.81	10.738%	$268.8829	$268.88	$268.90	$268.90
Purchase #4	$120.77	8.549%	$131.0946	$131.09	$131.10	$131.10
Purchase #5	$67.91	11.589%	$75.7801	$75.78	$75.80	$75.80
Purchase #6	$94.94	12.593%	$106.8958	$106.90	$106.90	$106.90
Purchase #7	$214.62	8.863%	$233.6418	$233.64	$233.65	$233.60
7 purchase totals =	$926.47		$1,015.2804	$1,015.28	$1,015.35	$1,015.30