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	$196.66	11.467%	$219.211	$219.21	$219.20	$219.20
Purchase #2	$47.57	9.769%	$52.2171	$52.22	$52.20	$52.20
Purchase #3	$49.60	5.229%	$52.1936	$52.19	$52.20	$52.20
Purchase #4	$29.65	11.663%	$33.1081	$33.11	$33.10	$33.10
Purchase #5	$191.33	4.298%	$199.5534	$199.55	$199.55	$199.60
Purchase #6	$74.75	4.356%	$78.0061	$78.01	$78.00	$78.00
Purchase #7	$52.46	7.757%	$56.5293	$56.53	$56.55	$56.50
7 purchase totals =	$642.02		$690.8186	$690.82	$690.80	$690.80