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	$175.52	6.601%	$187.1061	$187.11	$187.10	$187.10
Purchase #2	$45.39	9.821%	$49.8478	$49.85	$49.85	$49.80
Purchase #3	$36.79	9.714%	$40.3638	$40.36	$40.35	$40.40
Purchase #4	$14.32	4.868%	$15.0171	$15.02	$15.00	$15.00
Purchase #5	$61.63	5.248%	$64.8643	$64.86	$64.85	$64.90
Purchase #6	$119.69	9.827%	$131.4519	$131.45	$131.45	$131.50
Purchase #7	$171.94	6.111%	$182.4473	$182.45	$182.45	$182.40
7 purchase totals =	$625.28		$671.0983	$671.10	$671.05	$671.10