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	$172.72	7.331%	$185.3821	$185.38	$185.40	$185.40
Purchase #2	$108.43	10.172%	$119.4595	$119.46	$119.45	$119.50
Purchase #3	$30.38	5.601%	$32.0816	$32.08	$32.10	$32.10
Purchase #4	$200.70	12.260%	$225.3058	$225.31	$225.30	$225.30
Purchase #5	$86.93	5.523%	$91.7311	$91.73	$91.75	$91.70
Purchase #6	$64.71	4.287%	$67.4841	$67.48	$67.50	$67.50
Purchase #7	$123.36	7.532%	$132.6515	$132.65	$132.65	$132.70
7 purchase totals =	$787.23		$854.0957	$854.09	$854.15	$854.20