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	$92.49	12.475%	$104.0281	$104.03	$104.05	$104.00
Purchase #2	$93.41	5.595%	$98.6363	$98.64	$98.65	$98.60
Purchase #3	$70.71	11.791%	$79.0474	$79.05	$79.05	$79.00
Purchase #4	$163.83	12.173%	$183.773	$183.77	$183.75	$183.80
Purchase #5	$147.39	9.546%	$161.4598	$161.46	$161.45	$161.50
Purchase #6	$172.80	10.468%	$190.8887	$190.89	$190.90	$190.90
Purchase #7	$176.52	12.760%	$199.044	$199.04	$199.05	$199.00
7 purchase totals =	$917.15		$1,016.8773	$1,016.88	$1,016.90	$1,016.80