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	$80.83	10.464%	$89.2881	$89.29	$89.30	$89.30
Purchase #2	$125.41	6.493%	$133.5529	$133.55	$133.55	$133.60
Purchase #3	$146.26	6.851%	$156.2803	$156.28	$156.30	$156.30
Purchase #4	$228.88	7.448%	$245.927	$245.93	$245.95	$245.90
Purchase #5	$94.56	10.736%	$104.712	$104.71	$104.70	$104.70
Purchase #6	$217.75	11.493%	$242.776	$242.78	$242.80	$242.80
Purchase #7	$89.76	11.389%	$99.9828	$99.98	$100.00	$100.00
7 purchase totals =	$983.45		$1,072.5191	$1,072.52	$1,072.60	$1,072.60