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	$70.85	11.172%	$78.7654	$78.77	$78.75	$78.80
Purchase #2	$169.34	13.271%	$191.8131	$191.81	$191.80	$191.80
Purchase #3	$133.88	11.167%	$148.8304	$148.83	$148.85	$148.80
Purchase #4	$91.56	4.355%	$95.5474	$95.55	$95.55	$95.50
Purchase #5	$172.99	6.283%	$183.859	$183.86	$183.85	$183.90
Purchase #6	$174.62	7.274%	$187.3219	$187.32	$187.30	$187.30
Purchase #7	$203.76	3.272%	$210.427	$210.43	$210.45	$210.40
7 purchase totals =	$1,017.00		$1,096.5642	$1,096.57	$1,096.55	$1,096.50