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	$59.36	10.376%	$65.5192	$65.52	$65.50	$65.50
Purchase #2	$156.46	6.382%	$166.4453	$166.45	$166.45	$166.40
Purchase #3	$233.91	3.216%	$241.4325	$241.43	$241.45	$241.40
Purchase #4	$161.76	13.590%	$183.7432	$183.74	$183.75	$183.70
Purchase #5	$33.71	12.500%	$37.9238	$37.92	$37.90	$37.90
Purchase #6	$220.75	3.173%	$227.7544	$227.75	$227.75	$227.80
Purchase #7	$84.87	9.295%	$92.7587	$92.76	$92.75	$92.80
7 purchase totals =	$950.82		$1,015.5771	$1,015.57	$1,015.55	$1,015.50