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	$177.76	7.790%	$191.6075	$191.61	$191.60	$191.60
Purchase #2	$102.86	4.540%	$107.5298	$107.53	$107.55	$107.50
Purchase #3	$224.67	4.363%	$234.4724	$234.47	$234.45	$234.50
Purchase #4	$39.40	5.381%	$41.5201	$41.52	$41.50	$41.50
Purchase #5	$160.81	12.404%	$180.7569	$180.76	$180.75	$180.80
Purchase #6	$179.71	13.117%	$203.2826	$203.28	$203.30	$203.30
Purchase #7	$94.75	5.841%	$100.2843	$100.28	$100.30	$100.30
7 purchase totals =	$979.96		$1,059.4536	$1,059.45	$1,059.45	$1,059.50