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	$93.64	8.430%	$101.5339	$101.53	$101.55	$101.50
Purchase #2	$142.43	4.267%	$148.5075	$148.51	$148.50	$148.50
Purchase #3	$59.89	9.361%	$65.4963	$65.50	$65.50	$65.50
Purchase #4	$239.51	9.443%	$262.1269	$262.13	$262.15	$262.10
Purchase #5	$96.55	11.553%	$107.7044	$107.70	$107.70	$107.70
Purchase #6	$174.86	7.142%	$187.3485	$187.35	$187.35	$187.30
Purchase #7	$88.30	13.343%	$100.0819	$100.08	$100.10	$100.10
7 purchase totals =	$895.18		$972.7994	$972.80	$972.85	$972.70