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	$217.58	11.187%	$241.9207	$241.92	$241.90	$241.90
Purchase #2	$200.69	11.835%	$224.4417	$224.44	$224.45	$224.40
Purchase #3	$70.80	10.561%	$78.2772	$78.28	$78.30	$78.30
Purchase #4	$73.54	10.557%	$81.3036	$81.30	$81.30	$81.30
Purchase #5	$243.76	4.386%	$254.4513	$254.45	$254.45	$254.50
Purchase #6	$159.83	12.433%	$179.7017	$179.70	$179.70	$179.70
Purchase #7	$74.69	9.701%	$81.9357	$81.94	$81.95	$81.90
7 purchase totals =	$1,040.89		$1,142.0319	$1,142.03	$1,142.05	$1,142.00