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	$22.90	4.872%	$24.0157	$24.02	$24.00	$24.00
Purchase #2	$68.83	5.233%	$72.4319	$72.43	$72.45	$72.40
Purchase #3	$168.29	11.855%	$188.2408	$188.24	$188.25	$188.20
Purchase #4	$133.95	12.606%	$150.8357	$150.84	$150.85	$150.80
Purchase #5	$245.88	9.678%	$269.6763	$269.68	$269.70	$269.70
Purchase #6	$189.80	13.776%	$215.9468	$215.95	$215.95	$215.90
Purchase #7	$86.35	3.615%	$89.4716	$89.47	$89.45	$89.50
7 purchase totals =	$916.00		$1,010.6188	$1,010.63	$1,010.65	$1,010.50