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	$54.63	9.697%	$59.9275	$59.93	$59.95	$59.90
Purchase #2	$240.89	3.718%	$249.8463	$249.85	$249.85	$249.80
Purchase #3	$72.53	9.540%	$79.4494	$79.45	$79.45	$79.40
Purchase #4	$234.32	13.793%	$266.6398	$266.64	$266.65	$266.60
Purchase #5	$247.34	6.794%	$264.1443	$264.14	$264.15	$264.10
Purchase #6	$89.54	8.770%	$97.3927	$97.39	$97.40	$97.40
Purchase #7	$82.91	4.269%	$86.4494	$86.45	$86.45	$86.40
7 purchase totals =	$1,022.16		$1,103.8494	$1,103.85	$1,103.90	$1,103.60