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	$234.60	6.714%	$250.351	$250.35	$250.35	$250.40
Purchase #2	$206.76	5.216%	$217.5446	$217.54	$217.55	$217.50
Purchase #3	$153.60	10.357%	$169.5084	$169.51	$169.50	$169.50
Purchase #4	$131.56	12.426%	$147.9076	$147.91	$147.90	$147.90
Purchase #5	$191.25	4.653%	$200.1489	$200.15	$200.15	$200.10
Purchase #6	$54.83	3.253%	$56.6136	$56.61	$56.60	$56.60
Purchase #7	$38.60	4.191%	$40.2177	$40.22	$40.20	$40.20
7 purchase totals =	$1,011.20		$1,082.2918	$1,082.29	$1,082.25	$1,082.20