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	$152.88	3.697%	$158.532	$158.53	$158.55	$158.50
Purchase #2	$73.96	10.732%	$81.8974	$81.90	$81.90	$81.90
Purchase #3	$99.55	5.284%	$104.8102	$104.81	$104.80	$104.80
Purchase #4	$112.55	4.613%	$117.7419	$117.74	$117.75	$117.70
Purchase #5	$116.93	11.600%	$130.4939	$130.49	$130.50	$130.50
Purchase #6	$159.75	13.300%	$180.9968	$181.00	$181.00	$181.00
Purchase #7	$242.28	11.760%	$270.7721	$270.77	$270.75	$270.80
7 purchase totals =	$957.90		$1,045.2443	$1,045.24	$1,045.25	$1,045.20