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	$205.73	6.214%	$218.5141	$218.51	$218.50	$218.50
Purchase #2	$229.88	3.345%	$237.5695	$237.57	$237.55	$237.60
Purchase #3	$90.96	11.228%	$101.173	$101.17	$101.15	$101.20
Purchase #4	$80.53	13.731%	$91.5876	$91.59	$91.60	$91.60
Purchase #5	$105.75	6.484%	$112.6068	$112.61	$112.60	$112.60
Purchase #6	$133.79	7.753%	$144.1627	$144.16	$144.15	$144.20
Purchase #7	$178.94	7.260%	$191.931	$191.93	$191.95	$191.90
7 purchase totals =	$1,025.58		$1,097.5447	$1,097.54	$1,097.50	$1,097.60