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	$140.36	3.813%	$145.7119	$145.71	$145.70	$145.70
Purchase #2	$207.60	13.143%	$234.8849	$234.88	$234.90	$234.90
Purchase #3	$27.80	3.661%	$28.8178	$28.82	$28.80	$28.80
Purchase #4	$249.36	4.698%	$261.0749	$261.07	$261.05	$261.10
Purchase #5	$141.91	6.744%	$151.4804	$151.48	$151.50	$151.50
Purchase #6	$108.38	4.233%	$112.9677	$112.97	$112.95	$113.00
Purchase #7	$111.55	4.756%	$116.8553	$116.86	$116.85	$116.90
7 purchase totals =	$986.96		$1,051.7929	$1,051.79	$1,051.75	$1,051.90