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	$95.38	10.242%	$105.1488	$105.15	$105.15	$105.10
Purchase #2	$232.73	13.161%	$263.3596	$263.36	$263.35	$263.40
Purchase #3	$161.42	10.672%	$178.6467	$178.65	$178.65	$178.60
Purchase #4	$58.94	13.245%	$66.7466	$66.75	$66.75	$66.70
Purchase #5	$134.63	7.330%	$144.4984	$144.50	$144.50	$144.50
Purchase #6	$100.79	10.331%	$111.2026	$111.20	$111.20	$111.20
Purchase #7	$156.92	11.474%	$174.925	$174.93	$174.95	$174.90
7 purchase totals =	$940.81		$1,044.5277	$1,044.54	$1,044.55	$1,044.40