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	$249.43	7.459%	$268.035	$268.04	$268.05	$268.00
Purchase #2	$44.56	6.800%	$47.5901	$47.59	$47.60	$47.60
Purchase #3	$59.90	12.378%	$67.3144	$67.31	$67.30	$67.30
Purchase #4	$228.85	3.503%	$236.8666	$236.87	$236.85	$236.90
Purchase #5	$126.38	11.794%	$141.2853	$141.29	$141.30	$141.30
Purchase #6	$191.38	3.676%	$198.4151	$198.42	$198.40	$198.40
Purchase #7	$206.77	7.403%	$222.0772	$222.08	$222.10	$222.10
7 purchase totals =	$1,107.27		$1,181.5837	$1,181.60	$1,181.60	$1,181.60