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	$141.91	7.373%	$152.373	$152.37	$152.35	$152.40
Purchase #2	$96.29	5.703%	$101.7814	$101.78	$101.80	$101.80
Purchase #3	$213.69	11.311%	$237.8605	$237.86	$237.85	$237.90
Purchase #4	$130.52	9.359%	$142.7354	$142.74	$142.75	$142.70
Purchase #5	$209.56	9.333%	$229.1182	$229.12	$229.10	$229.10
Purchase #6	$79.82	13.801%	$90.836	$90.84	$90.85	$90.80
Purchase #7	$205.66	9.126%	$224.4285	$224.43	$224.45	$224.40
7 purchase totals =	$1,077.45		$1,179.1330	$1,179.14	$1,179.15	$1,179.10