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	$169.81	7.539%	$182.612	$182.61	$182.60	$182.60
Purchase #2	$169.29	9.316%	$185.0611	$185.06	$185.05	$185.10
Purchase #3	$88.28	3.229%	$91.1306	$91.13	$91.15	$91.10
Purchase #4	$134.94	3.149%	$139.1893	$139.19	$139.20	$139.20
Purchase #5	$20.29	4.128%	$21.1276	$21.13	$21.15	$21.10
Purchase #6	$212.84	3.162%	$219.57	$219.57	$219.55	$219.60
Purchase #7	$211.75	12.153%	$237.484	$237.48	$237.50	$237.50
7 purchase totals =	$1,007.20		$1,076.1746	$1,076.17	$1,076.20	$1,076.20