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	$230.73	11.566%	$257.4162	$257.42	$257.40	$257.40
Purchase #2	$129.73	9.135%	$141.5808	$141.58	$141.60	$141.60
Purchase #3	$106.74	5.787%	$112.917	$112.92	$112.90	$112.90
Purchase #4	$134.33	12.638%	$151.3066	$151.31	$151.30	$151.30
Purchase #5	$78.55	6.577%	$83.7162	$83.72	$83.70	$83.70
Purchase #6	$109.60	13.705%	$124.6207	$124.62	$124.60	$124.60
Purchase #7	$123.47	13.676%	$140.3558	$140.36	$140.35	$140.40
7 purchase totals =	$913.15		$1,011.9133	$1,011.93	$1,011.85	$1,011.90