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	$241.74	10.288%	$266.6102	$266.61	$266.60	$266.60
Purchase #2	$82.56	9.772%	$90.6278	$90.63	$90.65	$90.60
Purchase #3	$161.61	3.579%	$167.394	$167.39	$167.40	$167.40
Purchase #4	$238.74	10.118%	$262.8957	$262.90	$262.90	$262.90
Purchase #5	$147.60	11.215%	$164.1533	$164.15	$164.15	$164.20
Purchase #6	$47.35	10.453%	$52.2995	$52.30	$52.30	$52.30
Purchase #7	$29.31	13.392%	$33.2352	$33.24	$33.25	$33.20
7 purchase totals =	$948.91		$1,037.2157	$1,037.22	$1,037.25	$1,037.20