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	$143.37	9.442%	$156.907	$156.91	$156.90	$156.90
Purchase #2	$70.37	4.482%	$73.524	$73.52	$73.50	$73.50
Purchase #3	$67.41	7.363%	$72.3734	$72.37	$72.35	$72.40
Purchase #4	$222.40	10.201%	$245.087	$245.09	$245.10	$245.10
Purchase #5	$119.46	11.311%	$132.9721	$132.97	$132.95	$133.00
Purchase #6	$40.58	13.520%	$46.0664	$46.07	$46.05	$46.10
Purchase #7	$145.45	11.596%	$162.3164	$162.32	$162.30	$162.30
7 purchase totals =	$809.04		$889.2463	$889.25	$889.15	$889.30