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	$221.56	4.365%	$231.2311	$231.23	$231.25	$231.20
Purchase #2	$91.35	6.512%	$97.2987	$97.30	$97.30	$97.30
Purchase #3	$248.84	6.440%	$264.8653	$264.87	$264.85	$264.90
Purchase #4	$81.34	10.509%	$89.888	$89.89	$89.90	$89.90
Purchase #5	$196.35	8.369%	$212.7825	$212.78	$212.80	$212.80
Purchase #6	$64.74	10.610%	$71.6089	$71.61	$71.60	$71.60
Purchase #7	$104.90	10.828%	$116.2586	$116.26	$116.25	$116.30
7 purchase totals =	$1,009.08		$1,083.9331	$1,083.94	$1,083.95	$1,084.00