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	$149.78	8.322%	$162.2447	$162.24	$162.25	$162.20
Purchase #2	$69.38	13.599%	$78.815	$78.82	$78.80	$78.80
Purchase #3	$63.45	4.200%	$66.1149	$66.11	$66.10	$66.10
Purchase #4	$18.98	11.798%	$21.2193	$21.22	$21.20	$21.20
Purchase #5	$79.88	3.686%	$82.8244	$82.82	$82.80	$82.80
Purchase #6	$191.78	6.869%	$204.9534	$204.95	$204.95	$205.00
Purchase #7	$148.31	6.367%	$157.7529	$157.75	$157.75	$157.80
7 purchase totals =	$721.56		$773.9246	$773.91	$773.85	$773.90