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	$74.66	5.507%	$78.7715	$78.77	$78.75	$78.80
Purchase #2	$49.79	5.474%	$52.5155	$52.52	$52.50	$52.50
Purchase #3	$29.69	4.616%	$31.0605	$31.06	$31.05	$31.10
Purchase #4	$169.89	4.568%	$177.6506	$177.65	$177.65	$177.70
Purchase #5	$162.90	10.456%	$179.9328	$179.93	$179.95	$179.90
Purchase #6	$223.61	6.661%	$238.5047	$238.50	$238.50	$238.50
Purchase #7	$238.27	6.108%	$252.8235	$252.82	$252.80	$252.80
7 purchase totals =	$948.81		$1,011.2591	$1,011.25	$1,011.20	$1,011.30