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	$151.44	3.681%	$157.0145	$157.01	$157.00	$157.00
Purchase #2	$192.81	3.155%	$198.8932	$198.89	$198.90	$198.90
Purchase #3	$178.67	6.245%	$189.8279	$189.83	$189.85	$189.80
Purchase #4	$103.71	8.680%	$112.712	$112.71	$112.70	$112.70
Purchase #5	$191.89	9.642%	$210.392	$210.39	$210.40	$210.40
Purchase #6	$162.46	7.815%	$175.1562	$175.16	$175.15	$175.20
Purchase #7	$169.37	12.468%	$190.4871	$190.49	$190.50	$190.50
7 purchase totals =	$1,150.35		$1,234.4829	$1,234.48	$1,234.50	$1,234.50