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	$76.27	7.737%	$82.171	$82.17	$82.15	$82.20
Purchase #2	$128.61	6.104%	$136.4604	$136.46	$136.45	$136.50
Purchase #3	$159.59	9.567%	$174.858	$174.86	$174.85	$174.90
Purchase #4	$56.71	13.864%	$64.5723	$64.57	$64.55	$64.60
Purchase #5	$218.76	13.448%	$248.1788	$248.18	$248.20	$248.20
Purchase #6	$191.58	11.503%	$213.6174	$213.62	$213.60	$213.60
Purchase #7	$173.98	10.341%	$191.9713	$191.97	$191.95	$192.00
7 purchase totals =	$1,005.50		$1,111.8292	$1,111.83	$1,111.75	$1,112.00