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	$110.74	9.102%	$120.8196	$120.82	$120.80	$120.80
Purchase #2	$178.69	3.185%	$184.3813	$184.38	$184.40	$184.40
Purchase #3	$229.83	3.437%	$237.7293	$237.73	$237.75	$237.70
Purchase #4	$73.75	12.748%	$83.1517	$83.15	$83.15	$83.20
Purchase #5	$91.88	7.510%	$98.7802	$98.78	$98.80	$98.80
Purchase #6	$189.38	5.865%	$200.4871	$200.49	$200.50	$200.50
Purchase #7	$142.44	5.717%	$150.5833	$150.58	$150.60	$150.60
7 purchase totals =	$1,016.71		$1,075.9325	$1,075.93	$1,076.00	$1,076.00