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	$195.84	10.453%	$216.3112	$216.31	$216.30	$216.30
Purchase #2	$79.54	3.798%	$82.5609	$82.56	$82.55	$82.60
Purchase #3	$171.35	7.648%	$184.4548	$184.45	$184.45	$184.50
Purchase #4	$225.94	8.297%	$244.6862	$244.69	$244.70	$244.70
Purchase #5	$132.87	8.418%	$144.055	$144.06	$144.05	$144.10
Purchase #6	$145.70	3.488%	$150.782	$150.78	$150.80	$150.80
Purchase #7	$60.56	9.683%	$66.424	$66.42	$66.40	$66.40
7 purchase totals =	$1,011.80		$1,089.2741	$1,089.27	$1,089.25	$1,089.40