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	$198.30	8.666%	$215.4847	$215.48	$215.50	$215.50
Purchase #2	$30.64	4.225%	$31.9345	$31.93	$31.95	$31.90
Purchase #3	$128.82	9.204%	$140.6766	$140.68	$140.70	$140.70
Purchase #4	$53.43	12.543%	$60.1317	$60.13	$60.15	$60.10
Purchase #5	$216.41	4.632%	$226.4341	$226.43	$226.45	$226.40
Purchase #6	$170.88	10.289%	$188.4618	$188.46	$188.45	$188.50
Purchase #7	$203.91	6.870%	$217.9186	$217.92	$217.90	$217.90
7 purchase totals =	$1,002.39		$1,081.0420	$1,081.03	$1,081.10	$1,081.00