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	$183.94	3.461%	$190.3062	$190.31	$190.30	$190.30
Purchase #2	$56.97	5.274%	$59.9746	$59.97	$59.95	$60.00
Purchase #3	$227.62	9.595%	$249.4601	$249.46	$249.45	$249.50
Purchase #4	$139.95	8.833%	$152.3118	$152.31	$152.30	$152.30
Purchase #5	$155.38	4.410%	$162.2323	$162.23	$162.25	$162.20
Purchase #6	$55.65	7.740%	$59.9573	$59.96	$59.95	$60.00
Purchase #7	$190.74	7.553%	$205.1466	$205.15	$205.15	$205.10
7 purchase totals =	$1,010.25		$1,079.3889	$1,079.39	$1,079.35	$1,079.40