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	$80.54	7.250%	$86.3792	$86.38	$86.40	$86.40
Purchase #2	$235.94	8.311%	$255.549	$255.55	$255.55	$255.50
Purchase #3	$237.54	3.802%	$246.5713	$246.57	$246.55	$246.60
Purchase #4	$82.65	4.761%	$86.585	$86.59	$86.60	$86.60
Purchase #5	$106.62	6.802%	$113.8723	$113.87	$113.85	$113.90
Purchase #6	$234.49	12.705%	$264.282	$264.28	$264.30	$264.30
Purchase #7	$80.55	9.251%	$88.0017	$88.00	$88.00	$88.00
7 purchase totals =	$1,058.33		$1,141.2405	$1,141.24	$1,141.25	$1,141.30