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	$182.25	12.630%	$205.2682	$205.27	$205.25	$205.30
Purchase #2	$53.77	10.326%	$59.3223	$59.32	$59.30	$59.30
Purchase #3	$101.81	3.145%	$105.0119	$105.01	$105.00	$105.00
Purchase #4	$61.41	4.684%	$64.2864	$64.29	$64.30	$64.30
Purchase #5	$213.81	13.689%	$243.0785	$243.08	$243.10	$243.10
Purchase #6	$216.40	10.430%	$238.9705	$238.97	$238.95	$239.00
Purchase #7	$233.84	5.282%	$246.1914	$246.19	$246.20	$246.20
7 purchase totals =	$1,063.29		$1,162.1292	$1,162.13	$1,162.10	$1,162.20