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	$154.62	3.747%	$160.4136	$160.41	$160.40	$160.40
Purchase #2	$85.86	9.636%	$94.1335	$94.13	$94.15	$94.10
Purchase #3	$76.99	7.521%	$82.7804	$82.78	$82.80	$82.80
Purchase #4	$215.33	10.250%	$237.4013	$237.40	$237.40	$237.40
Purchase #5	$62.62	5.487%	$66.056	$66.06	$66.05	$66.10
Purchase #6	$125.71	9.680%	$137.8787	$137.88	$137.90	$137.90
Purchase #7	$245.77	3.865%	$255.269	$255.27	$255.25	$255.30
7 purchase totals =	$966.90		$1,033.9325	$1,033.93	$1,033.95	$1,034.00