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	$145.79	11.687%	$162.8285	$162.83	$162.85	$162.80
Purchase #2	$215.79	3.475%	$223.2887	$223.29	$223.30	$223.30
Purchase #3	$226.89	4.622%	$237.3769	$237.38	$237.40	$237.40
Purchase #4	$136.29	12.477%	$153.2949	$153.29	$153.30	$153.30
Purchase #5	$72.63	9.539%	$79.5582	$79.56	$79.55	$79.60
Purchase #6	$47.33	7.520%	$50.8892	$50.89	$50.90	$50.90
Purchase #7	$219.52	7.259%	$235.455	$235.46	$235.45	$235.50
7 purchase totals =	$1,064.24		$1,142.6914	$1,142.70	$1,142.75	$1,142.80