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	$27.68	3.837%	$28.7421	$28.74	$28.75	$28.70
Purchase #2	$182.90	8.472%	$198.3953	$198.40	$198.40	$198.40
Purchase #3	$161.55	9.148%	$176.3286	$176.33	$176.35	$176.30
Purchase #4	$172.91	4.686%	$181.0126	$181.01	$181.00	$181.00
Purchase #5	$99.39	12.365%	$111.6796	$111.68	$111.70	$111.70
Purchase #6	$162.53	5.490%	$171.4529	$171.45	$171.45	$171.50
Purchase #7	$145.81	13.403%	$165.3529	$165.35	$165.35	$165.40
7 purchase totals =	$952.77		$1,032.9640	$1,032.96	$1,033.00	$1,033.00