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	$119.89	6.170%	$127.2872	$127.29	$127.30	$127.30
Purchase #2	$116.48	12.120%	$130.5974	$130.60	$130.60	$130.60
Purchase #3	$168.36	10.728%	$186.4217	$186.42	$186.40	$186.40
Purchase #4	$8.61	11.786%	$9.6248	$9.62	$9.60	$9.60
Purchase #5	$172.38	11.804%	$192.7277	$192.73	$192.75	$192.70
Purchase #6	$185.61	13.617%	$210.8845	$210.88	$210.90	$210.90
Purchase #7	$140.80	9.705%	$154.4646	$154.46	$154.45	$154.50
7 purchase totals =	$912.13		$1,012.0079	$1,012.00	$1,012.00	$1,012.00