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	$156.86	11.157%	$174.3609	$174.36	$174.35	$174.40
Purchase #2	$124.96	4.775%	$130.9268	$130.93	$130.95	$130.90
Purchase #3	$181.64	10.550%	$200.803	$200.80	$200.80	$200.80
Purchase #4	$107.92	7.740%	$116.273	$116.27	$116.25	$116.30
Purchase #5	$162.36	3.284%	$167.6919	$167.69	$167.70	$167.70
Purchase #6	$140.94	5.375%	$148.5155	$148.52	$148.50	$148.50
Purchase #7	$176.59	13.551%	$200.5197	$200.52	$200.50	$200.50
7 purchase totals =	$1,051.27		$1,139.0908	$1,139.09	$1,139.05	$1,139.10