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	$87.96	11.842%	$98.3762	$98.38	$98.40	$98.40
Purchase #2	$220.75	3.863%	$229.2776	$229.28	$229.30	$229.30
Purchase #3	$166.84	5.236%	$175.5757	$175.58	$175.60	$175.60
Purchase #4	$158.58	12.205%	$177.9347	$177.93	$177.95	$177.90
Purchase #5	$65.92	7.735%	$71.0189	$71.02	$71.00	$71.00
Purchase #6	$103.86	5.485%	$109.5567	$109.56	$109.55	$109.60
Purchase #7	$148.78	5.240%	$156.5761	$156.58	$156.60	$156.60
7 purchase totals =	$952.69		$1,018.3159	$1,018.33	$1,018.40	$1,018.40