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	$199.43	13.570%	$226.4927	$226.49	$226.50	$226.50
Purchase #2	$105.59	10.694%	$116.8818	$116.88	$116.90	$116.90
Purchase #3	$123.36	12.770%	$139.1131	$139.11	$139.10	$139.10
Purchase #4	$243.72	13.157%	$275.7862	$275.79	$275.80	$275.80
Purchase #5	$181.64	10.280%	$200.3126	$200.31	$200.30	$200.30
Purchase #6	$167.94	13.126%	$189.9838	$189.98	$190.00	$190.00
Purchase #7	$59.63	13.523%	$67.6938	$67.69	$67.70	$67.70
7 purchase totals =	$1,081.31		$1,216.2640	$1,216.25	$1,216.30	$1,216.30