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	$160.34	4.765%	$167.9802	$167.98	$168.00	$168.00
Purchase #2	$181.33	13.371%	$205.5756	$205.58	$205.60	$205.60
Purchase #3	$156.31	6.646%	$166.6984	$166.70	$166.70	$166.70
Purchase #4	$245.55	13.567%	$278.8638	$278.86	$278.85	$278.90
Purchase #5	$94.45	6.478%	$100.5685	$100.57	$100.55	$100.60
Purchase #6	$24.82	7.511%	$26.6842	$26.68	$26.70	$26.70
Purchase #7	$104.59	13.662%	$118.8791	$118.88	$118.90	$118.90
7 purchase totals =	$967.39		$1,065.2498	$1,065.25	$1,065.30	$1,065.40