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	$250.36	7.805%	$269.9006	$269.90	$269.90	$269.90
Purchase #2	$41.27	6.217%	$43.8358	$43.84	$43.85	$43.80
Purchase #3	$53.37	3.709%	$55.3495	$55.35	$55.35	$55.30
Purchase #4	$82.97	9.212%	$90.6132	$90.61	$90.60	$90.60
Purchase #5	$94.92	6.650%	$101.2322	$101.23	$101.25	$101.20
Purchase #6	$178.60	11.261%	$198.7121	$198.71	$198.70	$198.70
Purchase #7	$233.85	12.161%	$262.2885	$262.29	$262.30	$262.30
7 purchase totals =	$935.34		$1,021.9319	$1,021.93	$1,021.95	$1,021.80