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	$146.32	12.618%	$164.7827	$164.78	$164.80	$164.80
Purchase #2	$28.41	11.234%	$31.6016	$31.60	$31.60	$31.60
Purchase #3	$141.34	6.198%	$150.1003	$150.10	$150.10	$150.10
Purchase #4	$132.60	5.813%	$140.308	$140.31	$140.30	$140.30
Purchase #5	$227.39	3.401%	$235.1235	$235.12	$235.10	$235.10
Purchase #6	$216.72	10.849%	$240.232	$240.23	$240.25	$240.20
Purchase #7	$171.67	4.647%	$179.6475	$179.65	$179.65	$179.60
7 purchase totals =	$1,064.45		$1,141.7956	$1,141.79	$1,141.80	$1,141.70