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	$208.93	7.730%	$225.0803	$225.08	$225.10	$225.10
Purchase #2	$187.31	6.575%	$199.6256	$199.63	$199.65	$199.60
Purchase #3	$165.46	8.259%	$179.1253	$179.13	$179.15	$179.10
Purchase #4	$64.76	11.678%	$72.3227	$72.32	$72.30	$72.30
Purchase #5	$200.73	4.577%	$209.9174	$209.92	$209.90	$209.90
Purchase #6	$102.60	9.302%	$112.1439	$112.14	$112.15	$112.10
Purchase #7	$82.41	12.540%	$92.7442	$92.74	$92.75	$92.70
7 purchase totals =	$1,012.20		$1,090.9594	$1,090.96	$1,091.00	$1,090.80