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	$73.31	4.596%	$76.6793	$76.68	$76.70	$76.70
Purchase #2	$127.25	4.120%	$132.4927	$132.49	$132.50	$132.50
Purchase #3	$112.90	5.457%	$119.061	$119.06	$119.05	$119.10
Purchase #4	$113.86	13.112%	$128.7893	$128.79	$128.80	$128.80
Purchase #5	$229.43	11.627%	$256.1058	$256.11	$256.10	$256.10
Purchase #6	$170.30	11.758%	$190.3239	$190.32	$190.30	$190.30
Purchase #7	$68.71	5.588%	$72.5495	$72.55	$72.55	$72.50
7 purchase totals =	$895.76		$976.0015	$976.00	$976.00	$976.00