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	$188.64	6.258%	$200.4451	$200.45	$200.45	$200.40
Purchase #2	$245.51	5.179%	$258.225	$258.23	$258.25	$258.20
Purchase #3	$147.99	4.550%	$154.7235	$154.72	$154.70	$154.70
Purchase #4	$23.39	8.867%	$25.464	$25.46	$25.45	$25.50
Purchase #5	$231.83	7.545%	$249.3216	$249.32	$249.30	$249.30
Purchase #6	$157.31	9.398%	$172.094	$172.09	$172.10	$172.10
Purchase #7	$56.72	12.197%	$63.6381	$63.64	$63.65	$63.60
7 purchase totals =	$1,051.39		$1,123.9113	$1,123.91	$1,123.90	$1,123.80