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	$235.27	5.619%	$248.4898	$248.49	$248.50	$248.50
Purchase #2	$227.63	9.676%	$249.6555	$249.66	$249.65	$249.70
Purchase #3	$25.71	6.819%	$27.4632	$27.46	$27.45	$27.50
Purchase #4	$116.82	9.622%	$128.0604	$128.06	$128.05	$128.10
Purchase #5	$112.89	9.327%	$123.4193	$123.42	$123.40	$123.40
Purchase #6	$174.45	9.285%	$190.6477	$190.65	$190.65	$190.60
Purchase #7	$170.45	10.730%	$188.7393	$188.74	$188.75	$188.70
7 purchase totals =	$1,063.22		$1,156.4752	$1,156.48	$1,156.45	$1,156.50