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	$112.84	13.839%	$128.4559	$128.46	$128.45	$128.50
Purchase #2	$116.35	7.685%	$125.2915	$125.29	$125.30	$125.30
Purchase #3	$103.93	9.192%	$113.4832	$113.48	$113.50	$113.50
Purchase #4	$167.84	7.144%	$179.8305	$179.83	$179.85	$179.80
Purchase #5	$210.77	8.712%	$229.1323	$229.13	$229.15	$229.10
Purchase #6	$100.37	9.489%	$109.8941	$109.89	$109.90	$109.90
Purchase #7	$185.83	12.465%	$208.9937	$208.99	$209.00	$209.00
7 purchase totals =	$997.93		$1,095.0812	$1,095.07	$1,095.15	$1,095.10