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	$189.25	4.837%	$198.404	$198.40	$198.40	$198.40
Purchase #2	$194.53	3.299%	$200.9475	$200.95	$200.95	$200.90
Purchase #3	$92.73	11.156%	$103.075	$103.08	$103.10	$103.10
Purchase #4	$163.32	13.595%	$185.5234	$185.52	$185.50	$185.50
Purchase #5	$130.30	9.754%	$143.0095	$143.01	$143.00	$143.00
Purchase #6	$74.80	3.312%	$77.2774	$77.28	$77.30	$77.30
Purchase #7	$150.40	6.552%	$160.2542	$160.25	$160.25	$160.30
7 purchase totals =	$995.33		$1,068.4910	$1,068.49	$1,068.50	$1,068.50