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	$172.28	8.785%	$187.4148	$187.41	$187.40	$187.40
Purchase #2	$76.39	11.605%	$85.2551	$85.26	$85.25	$85.30
Purchase #3	$53.34	3.189%	$55.041	$55.04	$55.05	$55.00
Purchase #4	$40.51	6.187%	$43.0164	$43.02	$43.00	$43.00
Purchase #5	$69.74	6.621%	$74.3575	$74.36	$74.35	$74.40
Purchase #6	$150.91	7.526%	$162.2675	$162.27	$162.25	$162.30
Purchase #7	$53.46	12.737%	$60.2692	$60.27	$60.25	$60.30
7 purchase totals =	$616.63		$667.6215	$667.63	$667.55	$667.70