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	$184.85	8.303%	$200.1981	$200.20	$200.20	$200.20
Purchase #2	$66.97	9.864%	$73.5759	$73.58	$73.60	$73.60
Purchase #3	$231.97	4.282%	$241.903	$241.90	$241.90	$241.90
Purchase #4	$147.81	8.798%	$160.8143	$160.81	$160.80	$160.80
Purchase #5	$82.78	9.709%	$90.8171	$90.82	$90.80	$90.80
Purchase #6	$34.39	6.758%	$36.7141	$36.71	$36.70	$36.70
Purchase #7	$242.36	3.512%	$250.8717	$250.87	$250.85	$250.90
7 purchase totals =	$991.13		$1,054.8942	$1,054.89	$1,054.85	$1,054.90