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	$79.26	5.360%	$83.5083	$83.51	$83.50	$83.50
Purchase #2	$206.90	12.418%	$232.5928	$232.59	$232.60	$232.60
Purchase #3	$154.54	11.336%	$172.0587	$172.06	$172.05	$172.10
Purchase #4	$86.29	10.675%	$95.5015	$95.50	$95.50	$95.50
Purchase #5	$42.71	8.295%	$46.2528	$46.25	$46.25	$46.30
Purchase #6	$23.30	6.408%	$24.7931	$24.79	$24.80	$24.80
Purchase #7	$153.33	11.706%	$171.2788	$171.28	$171.30	$171.30
7 purchase totals =	$746.33		$825.9860	$825.98	$826.00	$826.10