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	$152.65	10.170%	$168.1745	$168.17	$168.15	$168.20
Purchase #2	$194.48	6.694%	$207.4985	$207.50	$207.50	$207.50
Purchase #3	$241.30	11.509%	$269.0712	$269.07	$269.05	$269.10
Purchase #4	$146.32	13.748%	$166.4361	$166.44	$166.45	$166.40
Purchase #5	$175.33	7.300%	$188.1291	$188.13	$188.15	$188.10
Purchase #6	$175.74	13.443%	$199.3647	$199.36	$199.35	$199.40
Purchase #7	$189.71	5.587%	$200.3091	$200.31	$200.30	$200.30
7 purchase totals =	$1,275.53		$1,398.9832	$1,398.98	$1,398.95	$1,399.00