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	$211.59	10.363%	$233.5171	$233.52	$233.50	$233.50
Purchase #2	$236.74	5.453%	$249.6494	$249.65	$249.65	$249.60
Purchase #3	$154.83	13.600%	$175.8869	$175.89	$175.90	$175.90
Purchase #4	$45.97	5.220%	$48.3696	$48.37	$48.35	$48.40
Purchase #5	$164.75	9.776%	$180.856	$180.86	$180.85	$180.90
Purchase #6	$209.38	6.466%	$222.9185	$222.92	$222.90	$222.90
Purchase #7	$6.63	6.461%	$7.0584	$7.06	$7.05	$7.10
7 purchase totals =	$1,029.89		$1,118.2559	$1,118.27	$1,118.20	$1,118.30