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	$165.61	4.337%	$172.7925	$172.79	$172.80	$172.80
Purchase #2	$188.27	8.359%	$204.0075	$204.01	$204.00	$204.00
Purchase #3	$45.52	4.217%	$47.4396	$47.44	$47.45	$47.40
Purchase #4	$171.76	4.691%	$179.8173	$179.82	$179.80	$179.80
Purchase #5	$242.82	10.158%	$267.4857	$267.49	$267.50	$267.50
Purchase #6	$78.69	6.239%	$83.5995	$83.60	$83.60	$83.60
Purchase #7	$187.45	4.433%	$195.7597	$195.76	$195.75	$195.80
7 purchase totals =	$1,080.12		$1,150.9018	$1,150.91	$1,150.90	$1,150.90