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	$86.47	9.378%	$94.5792	$94.58	$94.60	$94.60
Purchase #2	$57.39	10.253%	$63.2742	$63.27	$63.25	$63.30
Purchase #3	$31.46	6.662%	$33.5559	$33.56	$33.55	$33.60
Purchase #4	$231.81	3.757%	$240.5191	$240.52	$240.50	$240.50
Purchase #5	$56.92	6.668%	$60.7154	$60.72	$60.70	$60.70
Purchase #6	$59.53	10.399%	$65.7205	$65.72	$65.70	$65.70
Purchase #7	$123.35	6.306%	$131.1285	$131.13	$131.15	$131.10
7 purchase totals =	$646.93		$689.4928	$689.50	$689.45	$689.50