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	$145.71	3.237%	$150.4266	$150.43	$150.45	$150.40
Purchase #2	$75.80	12.472%	$85.2538	$85.25	$85.25	$85.30
Purchase #3	$36.80	3.333%	$38.0265	$38.03	$38.05	$38.00
Purchase #4	$182.48	12.564%	$205.4068	$205.41	$205.40	$205.40
Purchase #5	$188.83	3.197%	$194.8669	$194.87	$194.85	$194.90
Purchase #6	$171.28	4.683%	$179.301	$179.30	$179.30	$179.30
Purchase #7	$225.42	10.159%	$248.3204	$248.32	$248.30	$248.30
7 purchase totals =	$1,026.32		$1,101.6020	$1,101.61	$1,101.60	$1,101.60