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	$94.30	5.555%	$99.5384	$99.54	$99.55	$99.50
Purchase #2	$194.38	8.422%	$210.7507	$210.75	$210.75	$210.80
Purchase #3	$61.46	9.252%	$67.1463	$67.15	$67.15	$67.10
Purchase #4	$86.77	5.538%	$91.5753	$91.58	$91.60	$91.60
Purchase #5	$246.99	4.700%	$258.5985	$258.60	$258.60	$258.60
Purchase #6	$96.73	4.231%	$100.8226	$100.82	$100.80	$100.80
Purchase #7	$191.94	10.622%	$212.3279	$212.33	$212.35	$212.30
7 purchase totals =	$972.57		$1,040.7597	$1,040.77	$1,040.80	$1,040.70