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	$184.42	10.841%	$204.413	$204.41	$204.40	$204.40
Purchase #2	$165.74	9.606%	$181.661	$181.66	$181.65	$181.70
Purchase #3	$135.91	3.749%	$141.0053	$141.01	$141.00	$141.00
Purchase #4	$171.28	4.758%	$179.4295	$179.43	$179.45	$179.40
Purchase #5	$92.51	10.229%	$101.9728	$101.97	$101.95	$102.00
Purchase #6	$74.92	4.791%	$78.5094	$78.51	$78.50	$78.50
Purchase #7	$218.74	11.336%	$243.5364	$243.54	$243.55	$243.50
7 purchase totals =	$1,043.52		$1,130.5274	$1,130.53	$1,130.50	$1,130.50