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	$35.62	4.111%	$37.0843	$37.08	$37.10	$37.10
Purchase #2	$65.48	3.682%	$67.891	$67.89	$67.90	$67.90
Purchase #3	$22.26	4.867%	$23.3434	$23.34	$23.35	$23.30
Purchase #4	$72.80	10.365%	$80.3457	$80.35	$80.35	$80.30
Purchase #5	$9.42	7.498%	$10.1263	$10.13	$10.15	$10.10
Purchase #6	$123.41	7.338%	$132.4658	$132.47	$132.45	$132.50
Purchase #7	$45.46	4.541%	$47.5243	$47.52	$47.50	$47.50
7 purchase totals =	$374.45		$398.7808	$398.78	$398.80	$398.70