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	$150.29	13.816%	$171.0541	$171.05	$171.05	$171.10
Purchase #2	$97.30	3.534%	$100.7386	$100.74	$100.75	$100.70
Purchase #3	$178.39	5.582%	$188.3477	$188.35	$188.35	$188.30
Purchase #4	$7.26	8.705%	$7.892	$7.89	$7.90	$7.90
Purchase #5	$215.30	10.674%	$238.2811	$238.28	$238.30	$238.30
Purchase #6	$240.65	8.568%	$261.2689	$261.27	$261.25	$261.30
Purchase #7	$165.71	6.341%	$176.2177	$176.22	$176.20	$176.20
7 purchase totals =	$1,054.90		$1,143.8001	$1,143.80	$1,143.80	$1,143.80