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	$250.28	9.222%	$273.3608	$273.36	$273.35	$273.40
Purchase #2	$134.88	13.220%	$152.7111	$152.71	$152.70	$152.70
Purchase #3	$67.82	6.523%	$72.2439	$72.24	$72.25	$72.20
Purchase #4	$60.60	7.812%	$65.3341	$65.33	$65.35	$65.30
Purchase #5	$167.29	13.786%	$190.3526	$190.35	$190.35	$190.40
Purchase #6	$68.37	10.815%	$75.7642	$75.76	$75.75	$75.80
Purchase #7	$187.84	6.616%	$200.2675	$200.27	$200.25	$200.30
7 purchase totals =	$937.08		$1,030.0342	$1,030.02	$1,030.00	$1,030.10