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	$83.31	3.642%	$86.3442	$86.34	$86.35	$86.30
Purchase #2	$56.82	12.669%	$64.0185	$64.02	$64.00	$64.00
Purchase #3	$246.62	13.477%	$279.857	$279.86	$279.85	$279.90
Purchase #4	$196.74	9.607%	$215.6408	$215.64	$215.65	$215.60
Purchase #5	$141.65	12.688%	$159.6226	$159.62	$159.60	$159.60
Purchase #6	$117.65	11.698%	$131.4127	$131.41	$131.40	$131.40
Purchase #7	$79.40	11.280%	$88.3563	$88.36	$88.35	$88.40
7 purchase totals =	$922.19		$1,025.2521	$1,025.25	$1,025.20	$1,025.20