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	$160.96	6.543%	$171.4916	$171.49	$171.50	$171.50
Purchase #2	$63.27	3.172%	$65.2769	$65.28	$65.30	$65.30
Purchase #3	$146.42	9.553%	$160.4075	$160.41	$160.40	$160.40
Purchase #4	$85.97	13.612%	$97.6722	$97.67	$97.65	$97.70
Purchase #5	$189.58	10.521%	$209.5257	$209.53	$209.55	$209.50
Purchase #6	$100.59	3.794%	$104.4064	$104.41	$104.40	$104.40
Purchase #7	$123.90	7.763%	$133.5184	$133.52	$133.50	$133.50
7 purchase totals =	$870.69		$942.2987	$942.31	$942.30	$942.30