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	$47.99	12.120%	$53.8064	$53.81	$53.80	$53.80
Purchase #2	$96.51	3.502%	$99.8898	$99.89	$99.90	$99.90
Purchase #3	$103.88	12.266%	$116.6219	$116.62	$116.60	$116.60
Purchase #4	$228.57	7.576%	$245.8865	$245.89	$245.90	$245.90
Purchase #5	$189.76	3.115%	$195.671	$195.67	$195.65	$195.70
Purchase #6	$168.33	8.269%	$182.2492	$182.25	$182.25	$182.20
Purchase #7	$123.42	12.690%	$139.082	$139.08	$139.10	$139.10
7 purchase totals =	$958.46		$1,033.2068	$1,033.21	$1,033.20	$1,033.20