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	$187.90	6.657%	$200.4085	$200.41	$200.40	$200.40
Purchase #2	$234.45	4.819%	$245.7481	$245.75	$245.75	$245.70
Purchase #3	$57.96	3.815%	$60.1712	$60.17	$60.15	$60.20
Purchase #4	$81.56	9.766%	$89.5251	$89.53	$89.55	$89.50
Purchase #5	$60.25	5.398%	$63.5023	$63.50	$63.50	$63.50
Purchase #6	$193.62	11.349%	$215.5939	$215.59	$215.60	$215.60
Purchase #7	$200.81	13.478%	$227.8752	$227.88	$227.90	$227.90
7 purchase totals =	$1,016.55		$1,102.8243	$1,102.83	$1,102.85	$1,102.80