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	$154.70	11.654%	$172.7287	$172.73	$172.75	$172.70
Purchase #2	$119.33	6.767%	$127.4051	$127.41	$127.40	$127.40
Purchase #3	$199.29	9.175%	$217.5749	$217.57	$217.55	$217.60
Purchase #4	$98.94	13.295%	$112.0941	$112.09	$112.10	$112.10
Purchase #5	$25.45	7.262%	$27.2982	$27.30	$27.30	$27.30
Purchase #6	$94.98	6.721%	$101.3636	$101.36	$101.35	$101.40
Purchase #7	$172.98	3.747%	$179.4616	$179.46	$179.45	$179.50
7 purchase totals =	$865.67		$937.9262	$937.92	$937.90	$938.00