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	$104.54	10.309%	$115.317	$115.32	$115.30	$115.30
Purchase #2	$149.86	4.382%	$156.4269	$156.43	$156.45	$156.40
Purchase #3	$175.43	3.479%	$181.5332	$181.53	$181.55	$181.50
Purchase #4	$210.87	8.360%	$228.4987	$228.50	$228.50	$228.50
Purchase #5	$218.95	12.547%	$246.4217	$246.42	$246.40	$246.40
Purchase #6	$107.27	4.137%	$111.7078	$111.71	$111.70	$111.70
Purchase #7	$12.79	10.482%	$14.1306	$14.13	$14.15	$14.10
7 purchase totals =	$979.71		$1,054.0359	$1,054.04	$1,054.05	$1,053.90