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	$205.87	7.142%	$220.5732	$220.57	$220.55	$220.60
Purchase #2	$174.40	8.469%	$189.1699	$189.17	$189.15	$189.20
Purchase #3	$6.46	10.221%	$7.1203	$7.12	$7.10	$7.10
Purchase #4	$210.85	12.464%	$237.1303	$237.13	$237.15	$237.10
Purchase #5	$190.78	9.747%	$209.3753	$209.38	$209.40	$209.40
Purchase #6	$40.83	10.848%	$45.2592	$45.26	$45.25	$45.30
Purchase #7	$128.50	8.297%	$139.1616	$139.16	$139.15	$139.20
7 purchase totals =	$957.69		$1,047.7898	$1,047.79	$1,047.75	$1,047.90