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	$139.40	8.812%	$151.6839	$151.68	$151.70	$151.70
Purchase #2	$215.97	9.755%	$237.0379	$237.04	$237.05	$237.00
Purchase #3	$101.37	10.234%	$111.7442	$111.74	$111.75	$111.70
Purchase #4	$209.30	7.373%	$224.7317	$224.73	$224.75	$224.70
Purchase #5	$34.61	8.216%	$37.4536	$37.45	$37.45	$37.50
Purchase #6	$28.32	11.282%	$31.5151	$31.52	$31.50	$31.50
Purchase #7	$59.48	12.824%	$67.1077	$67.11	$67.10	$67.10
7 purchase totals =	$788.45		$861.2741	$861.27	$861.30	$861.20