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	$243.50	10.696%	$269.5448	$269.54	$269.55	$269.50
Purchase #2	$128.35	6.802%	$137.0804	$137.08	$137.10	$137.10
Purchase #3	$142.26	9.221%	$155.3778	$155.38	$155.40	$155.40
Purchase #4	$218.50	7.272%	$234.3893	$234.39	$234.40	$234.40
Purchase #5	$144.38	6.506%	$153.7734	$153.77	$153.75	$153.80
Purchase #6	$92.35	3.404%	$95.4936	$95.49	$95.50	$95.50
Purchase #7	$77.82	10.377%	$85.8954	$85.90	$85.90	$85.90
7 purchase totals =	$1,047.16		$1,131.5547	$1,131.55	$1,131.60	$1,131.60