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	$179.26	3.365%	$185.2921	$185.29	$185.30	$185.30
Purchase #2	$94.61	6.199%	$100.4749	$100.47	$100.45	$100.50
Purchase #3	$225.38	3.730%	$233.7867	$233.79	$233.80	$233.80
Purchase #4	$142.45	10.649%	$157.6195	$157.62	$157.60	$157.60
Purchase #5	$242.28	13.614%	$275.264	$275.26	$275.25	$275.30
Purchase #6	$94.89	4.207%	$98.882	$98.88	$98.90	$98.90
Purchase #7	$107.62	3.192%	$111.0552	$111.06	$111.05	$111.10
7 purchase totals =	$1,086.49		$1,162.3744	$1,162.37	$1,162.35	$1,162.50