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	$127.71	10.218%	$140.7594	$140.76	$140.75	$140.80
Purchase #2	$36.96	4.471%	$38.6125	$38.61	$38.60	$38.60
Purchase #3	$69.62	4.547%	$72.7856	$72.79	$72.80	$72.80
Purchase #4	$237.40	3.363%	$245.3838	$245.38	$245.40	$245.40
Purchase #5	$231.65	5.113%	$243.4943	$243.49	$243.50	$243.50
Purchase #6	$180.93	10.858%	$200.5754	$200.58	$200.60	$200.60
Purchase #7	$81.72	5.138%	$85.9188	$85.92	$85.90	$85.90
7 purchase totals =	$965.99		$1,027.5298	$1,027.53	$1,027.55	$1,027.60