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	$35.87	8.545%	$38.9351	$38.94	$38.95	$38.90
Purchase #2	$141.84	8.855%	$154.3999	$154.40	$154.40	$154.40
Purchase #3	$79.87	13.818%	$90.9064	$90.91	$90.90	$90.90
Purchase #4	$180.74	4.740%	$189.3071	$189.31	$189.30	$189.30
Purchase #5	$127.94	6.596%	$136.3789	$136.38	$136.40	$136.40
Purchase #6	$150.73	12.473%	$169.5306	$169.53	$169.55	$169.50
Purchase #7	$161.32	4.803%	$169.0682	$169.07	$169.05	$169.10
7 purchase totals =	$878.31		$948.5262	$948.54	$948.55	$948.50