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	$245.90	9.665%	$269.6662	$269.67	$269.65	$269.70
Purchase #2	$92.71	10.296%	$102.2554	$102.26	$102.25	$102.30
Purchase #3	$135.67	5.333%	$142.9053	$142.91	$142.90	$142.90
Purchase #4	$105.70	3.544%	$109.446	$109.45	$109.45	$109.40
Purchase #5	$125.90	8.763%	$136.9326	$136.93	$136.95	$136.90
Purchase #6	$146.34	12.610%	$164.7935	$164.79	$164.80	$164.80
Purchase #7	$209.42	9.810%	$229.9641	$229.96	$229.95	$230.00
7 purchase totals =	$1,061.64		$1,155.9631	$1,155.97	$1,155.95	$1,156.00