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	$96.27	13.638%	$109.3993	$109.40	$109.40	$109.40
Purchase #2	$92.99	10.443%	$102.7009	$102.70	$102.70	$102.70
Purchase #3	$137.44	3.392%	$142.102	$142.10	$142.10	$142.10
Purchase #4	$107.95	13.659%	$122.6949	$122.69	$122.70	$122.70
Purchase #5	$37.79	12.408%	$42.479	$42.48	$42.50	$42.50
Purchase #6	$204.59	10.193%	$225.4439	$225.44	$225.45	$225.40
Purchase #7	$245.39	13.751%	$279.1336	$279.13	$279.15	$279.10
7 purchase totals =	$922.42		$1,023.9536	$1,023.94	$1,024.00	$1,023.90