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	$157.50	6.663%	$167.9942	$167.99	$168.00	$168.00
Purchase #2	$212.28	9.791%	$233.0643	$233.06	$233.05	$233.10
Purchase #3	$14.64	6.681%	$15.6181	$15.62	$15.60	$15.60
Purchase #4	$191.48	4.858%	$200.7821	$200.78	$200.80	$200.80
Purchase #5	$160.42	7.447%	$172.3665	$172.37	$172.35	$172.40
Purchase #6	$197.91	4.377%	$206.5725	$206.57	$206.55	$206.60
Purchase #7	$91.94	13.727%	$104.5606	$104.56	$104.55	$104.60
7 purchase totals =	$1,026.17		$1,100.9583	$1,100.95	$1,100.90	$1,101.10