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	$105.72	6.182%	$112.2556	$112.26	$112.25	$112.30
Purchase #2	$232.64	9.672%	$255.1409	$255.14	$255.15	$255.10
Purchase #3	$34.58	5.123%	$36.3515	$36.35	$36.35	$36.40
Purchase #4	$210.90	10.677%	$233.4178	$233.42	$233.40	$233.40
Purchase #5	$141.58	4.277%	$147.6354	$147.64	$147.65	$147.60
Purchase #6	$81.96	12.676%	$92.3492	$92.35	$92.35	$92.30
Purchase #7	$175.98	10.429%	$194.333	$194.33	$194.35	$194.30
7 purchase totals =	$983.36		$1,071.4834	$1,071.49	$1,071.50	$1,071.40