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	$248.90	4.420%	$259.9014	$259.90	$259.90	$259.90
Purchase #2	$83.31	6.263%	$88.5277	$88.53	$88.55	$88.50
Purchase #3	$213.52	5.445%	$225.1462	$225.15	$225.15	$225.10
Purchase #4	$161.85	10.618%	$179.0352	$179.04	$179.05	$179.00
Purchase #5	$175.59	3.802%	$182.2659	$182.27	$182.25	$182.30
Purchase #6	$55.63	3.311%	$57.4719	$57.47	$57.45	$57.50
Purchase #7	$236.71	10.684%	$262.0001	$262.00	$262.00	$262.00
7 purchase totals =	$1,175.51		$1,254.3484	$1,254.36	$1,254.35	$1,254.30