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	$140.33	10.349%	$154.8528	$154.85	$154.85	$154.90
Purchase #2	$188.52	5.428%	$198.7529	$198.75	$198.75	$198.80
Purchase #3	$85.66	3.736%	$88.8603	$88.86	$88.85	$88.90
Purchase #4	$196.53	13.321%	$222.7098	$222.71	$222.70	$222.70
Purchase #5	$138.65	5.473%	$146.2383	$146.24	$146.25	$146.20
Purchase #6	$136.30	4.593%	$142.5603	$142.56	$142.55	$142.60
Purchase #7	$154.28	6.438%	$164.2125	$164.21	$164.20	$164.20
7 purchase totals =	$1,040.27		$1,118.1869	$1,118.18	$1,118.15	$1,118.30