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	$142.53	9.650%	$156.2841	$156.28	$156.30	$156.30
Purchase #2	$94.68	6.261%	$100.6079	$100.61	$100.60	$100.60
Purchase #3	$81.31	6.169%	$86.326	$86.33	$86.35	$86.30
Purchase #4	$245.73	13.535%	$278.9896	$278.99	$279.00	$279.00
Purchase #5	$224.31	6.658%	$239.2446	$239.24	$239.25	$239.20
Purchase #6	$81.40	4.833%	$85.3341	$85.33	$85.35	$85.30
Purchase #7	$243.94	13.140%	$275.9937	$275.99	$276.00	$276.00
7 purchase totals =	$1,113.90		$1,222.7800	$1,222.77	$1,222.85	$1,222.70