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	$231.52	4.287%	$241.4453	$241.45	$241.45	$241.40
Purchase #2	$74.70	6.453%	$79.5204	$79.52	$79.50	$79.50
Purchase #3	$178.31	3.659%	$184.8344	$184.83	$184.85	$184.80
Purchase #4	$123.71	3.242%	$127.7207	$127.72	$127.70	$127.70
Purchase #5	$183.80	4.764%	$192.5562	$192.56	$192.55	$192.60
Purchase #6	$106.94	12.719%	$120.5417	$120.54	$120.55	$120.50
Purchase #7	$110.82	3.643%	$114.8572	$114.86	$114.85	$114.90
7 purchase totals =	$1,009.80		$1,061.4759	$1,061.48	$1,061.45	$1,061.40